Cu12-xNixSb4S13 (x = 0, 0.05, 0.2, 0.5) tetrahedrites were synthesized by the polyol method. Measurements of magnetic susceptibility, specific heat capacity as well as electrical and thermal transport properties indicated a structural phase transition (SPT) of 1st order at Tk = 75-85 K, which is accompanied by strong changes in electronic density of states (EDOS) and entropy for x = 0, 0.05, and 0.2, whereas only weak changes were observed at x = 0.5. However, further temperature-dependent synchrotron high-resolution powder X-ray diffraction (HR PXRD) studies revealed compounds with Ni-content x = 0 and 0.5 to remain body-centered cubic [space group (SG) I43m, a approximate to 10.4(1) angstrom] down to 10 K, whereas crystal structures of x = 0.05 and 0.2 became tetragonal (SG P4c2, , ctetr approximate to acub) below Tk. Comparing changes of EDOS at the Fermi level [Delta N(EF)] deduced from magnetic and thermodynamic data with those calculated from density functional theory (DFT) in a rigid-band approximation, we found that decreases with Ni content and vanishes for x = 0.5, thus explaining the absence of the tetragonal instability at higher Ni dopings. This study shows that the SPT in tetrahedrites is facilitated by the presence of a minor amount of dopant.

The composition of a natural single crystalline specimen from the province of Potosí in Bolivia is found to be Fe0.8Mn0.2WO4. It crystallizes with the primitive monoclinic NiWO4 structure type [space group P2/c, a = 4.74751(6) Å, b = 5.71335(7) Å, c = 4.96847(5) Å, β = 90.15(1)°]. Magnetic susceptibility and specific heat capacity measurements indicated that the mineral undergoes multiple magnetic transitions: TN1 ≈ T\,cpN1 = 67(1) K, TN2 = 28(3) K, and T\,cpN2 = 8(1) K. The reduced magnetic entropy of ≈R ln 3 upon the high-temperature antiferromagnetic ordering suggests the failure of the simplified LS-coupling scheme in the description of the magnetism. Fe0.8Mn0.2WO4 is characterized by enlarged electrical resistivity showing an exponential decrease with temperature for T > 300 K, from which an energy gap of 310 meV is deduced. The well-pronounced maximum occurring in the phononic thermal conductivity just below the TN1 is described by the Debye-Callaway model, indicating the dominance of phonon scattering on defects as well as umklapp processes.

Yb5Rh6Sn18 crystallizes with a unique structural arrangement [space group P42/nmc, a = 9.6997(4) & Aring;, c = 13.7710(7) & Aring;], which is related with primitive cubic Yb3Rh4Sn13 and body-centered tetragonal (Sn1-xTbx)Tb4Rh6Sn18 types. X-ray absorption spectroscopy showed that Yb atoms exhibit temperature-dependent valence fluctuations (VF) (i.e., intermediate valence state). Its complex mechanism is corroborated by the fact that the well-pronounced maximum in magnetic susceptibility can only be fairly described by the Bickers-Cox-Wilkins model developed for a J = 3/2 multiplet, atypical for Yb ions. Both Hall and Seebeck coefficients revealed a switch of the sign, indicating the change of charge carrier type from electrons to holes between 120 and 220 K. Both these effects together with electrical resistivity and theoretical DFT calculations confirm Yb5Rh6Sn18 to be a metal, which disobeys the free electron gas theory. 'Rattling' motion of Sn1 atoms within the enlarged 16-vertices distorted Frank-Kasper polyhedra, concluded from the specific heat measurements, is argued to be the main reason for the appearance of a phonon resonance behavior, resulting in an ultra-low thermal conductivity in the studied stannide.

In the Yb-Co-Sn system a Remeika phase Yb3+xCo4Sn13-x is found with solid solution extending within 0 <= x 0.5. All these compounds crystallize with primitive cubic (space group Pm3n, a approximate to 9.54 angstrom) strongly disordered Sc3Ir4Si13+x type. Stoichiometric Yb3Co4Sn13 is a superconductor with critical temperature Tc = 3.1(2) K, lower- [Bc1 = 1.90(2) mT] and upper [Bc2 = 2.16(5) T] critical fields. The specific-heat jump Delta cp/gamma Tc = 1.72(9) together with the fact that Bc2(Tc) dependence is described by the Werthamer-Helfand-Hohenberg (WHH) model hint toward a conventional mechanism with a weak electron-phonon coupling. Although a more precise analysis is hampered by the presence of multiple superconducting transitions observed in the specific heat of this Remeika phase, the nonstoichiometric Yb3.2Co4Sn12.8 reveals Tc = 2.4(2) K and Bc2 = 4.79(9) T exceeding the classical Pauli limit. Strong electron-phonon coupling in this superconductor is confirmed by the high value of the lambda AD = 0.92(2) parameter determined from the Allen-Dynes formula. However, the electronic specific heat of Yb3.2Co4Sn12.8 follows the exponential law [cel(T ) proportional to e-Delta(0)/kBT ] and can be described by the alpha-model [alpha equivalent to Delta(0)/kBTc = 2] indicating this stannide to be a conventional BCS-superconductor. Both Yb3+xCo4Sn13-x (x = 0, 0.2) compounds reveal complex phonon spectra with possible "rattling" behavior. They are also found to be metallic systems, some aspects of which can be described by a free-electron-gas model.

Chirality in quantum materials is a topic of significant importance due to its profound effects on the electronic, magnetic, and optical properties of these systems. However, it is non-trivial to decouple the behavior of two enantiomorphs within the same material – perhaps explaining why the influence of chirality on electrical properties has remained largely unexplored. In this work, we examine the electrical conductivity, magnetoresistance, and thermal expansion coefficient of LaRhC_2 – a compound with a chiral crystal structure (tetragonal symmetry, space groups P4_1 or P4_3). The identification of a suitable monochiral domain was achieved via electron backscatter diffraction, which simultaneously determines crystallographic orientation and handedness. Both enantiomorphs are confirmed by single-crystal X-ray diffraction on monochiral specimens. The analysis of electrical resistivity was made possible through the single-domain extraction of enantiopure specimens from a polycrystalline sample using focused ion beam techniques. We establish that LaRhC_2 is a semiconductor with band gaps of approximately 20 meV and 33 meV parallel and perpendicular to the fourfold screw axis of the crystal structure, respectively – consistent with band structure calculations. A significant anisotropy is also observed in the thermal expansion, electrical resistivity as well as angular-dependent magnetoresistance parallel and perpendicular o [001] crystallographic directions.

Pseudo-ternary solid solutions, Lu(Ni1-xCox)C2 (0≤ x ≤1), were studied by means of powder X-ray diffraction, differential thermal analysis as well as electrical resistivity and heat capacity measurements. The crystal structure of the Lu(Ni1-xCox)C2 series, as investigated by means of X-ray powder diffraction, is structure type CeNiC2, space group Amm2, Pearson symbol oS8. The structural analysis reveals a non-monotonous evolution, in particular for the a- and c-lattice parameters, resulting in a non-linear decrease of the unit cell volume, markedly deviating from Vegard’s rule, due to non-isoelectronic substitution of Ni by Co. Utilizing differential thermal analysis (DTA) data, a pseudo-binary phase diagram LuNiC2–LuCoC2 has been constructed. The evolution of charge density wave order in Lu(Ni1-xCox)C2, which reaches an ordering temperature TCDW ≅ 450K for LuNiC2, was studied by means of electrical resistivity and heat capacity measurements. For solid solutions prepared via the floating-zone melting technique it became feasible to trace charge density wave (CDW) features of the temperature dependent electrical resistivity, thus, indicating a critical composition for the suppression of CDW order in Lu(Ni1-xCox)C2 at around x ≈ 0.15 – 0.17, which matches with a distinct drop of the composition dependent electronic Sommerfeld coefficient of the low temperature heat capacity of Ni-rich solid solutions.

Ternary carbides R2Ni5C3 (R = La-Nd, Sm, Gd, Tb) are the only representatives of the family of interstitial carbides (i.e., compounds with the composition RxTyCz, where T is a transition metal and 2 <= (x + y)/z <= 4). The crystal structures (space group P4/mbm) of Sm2Ni5C3 [a = 8.26131(7) angstrom, c = 3.89090(4) angstrom, RB = 3.2 %, Rp = 1.3 %] and Gd2Ni5C3 [a = 8.24683(4) angstrom, c = 3.85398(2) angstrom, RB = 3.9 %, Rp = 3.6 %] are refined for the first time. They are considered to be built by distorted [R8]-cubes incorporating [CNi6]-octahedra condensed with [C2R8]-trigonal bi-prisms. The structural units are characteristic of the CaTiO3- and AlB2-prototypes, respectively. Temperature dependencies of the magnetic susceptibility, specific heat, electrical resistivity, thermal conduc-tivity, and thermopower in the range 1.8 K (2 K) - 300 K are studied. R2Ni5C3 with R = Nd, Sm, Gd, order antiferromagnetically at TN = 3.4, 6.6, and 22.2 K, respectively. The nature of magnetic transitions in Ce2Ni5C3 at Tmag = 2.3 K and Tb2Ni5C3 at 29.4 K requires further clarification. No magnetic orderings for La2Ni5C3 (Pauli paramagnetic) and Pr2Ni5C3 (Curie-Weiss/van Vleck paramagnetic) are detected. Relatively high electrical resistivities and thermal conductivities, together with the small absolute values of Seebeck coefficients, result in poor thermoelectric performance of the R2Ni5C3 carbides. The calculated electronic structure for La2Ni5C3 indicated a rather low density of states at the Fermi level as well as its extreme sensitivity to any doping. The stabilization of the R2Ni5C3 interstitial carbides up to R = Tb is discussed assuming the rigid-band approach as well as the analysis of selected Ni-C interatomic distances.

Structural and physical properties of the Yb3Rh4Sn13 Remeika phase are investigated on large single crys-tals grown from Sn-flux. It crystallizes with disordered Y3Co4Ge13 structure type [space group Pm3 over bar n, a = 9.6709(2) angstrom], where the 24k crystallographic site occupied by Sn atoms is split. Yb3Rh4Sn13 is a superconductor (SC) with the critical temperature Tc = 7.63(5) K, lower [Bc1 = 14.5(5) mT] and upper [Bc2(0) = 2.89(5) T] critical fields, as well as a clear peak effect with B*(0) = 1.96(9) T observed in the M(H) loops. Bc2(Tc) can be described by the sum of two Werthamer-Helfand-Hohenberg equations. A gamma(B) proportional to B0.75 dependency is found. The electronic specific heat below Tc follows an exponential function including 87% of a strongly coupled [⠃1/kBTc = 3.52(1)] and 13% of a conventional s-wave-like [⠃2/kBTc = 1.32(1)] gap. The observations are in line with Yb3Rh4Sn13 being a two-gap SC. The Remeika phase reveals a complex electronic band structure studied by Hall coefficient (RH) measurements and calculations performed within the density functional theory. A "rattling" effect in Yb3Rh4Sn13 is discussed based on structural refinements and phononic contributions to its specific heat capacity.

X-ray diffraction and energy dispersive x-ray spectroscopic analyses showed a natural galena (PbS) crystal from Freiberg in Saxony (Germany) to be a single phase specimen [rock salt (NaCl) structure type, space group Fm3m, a = 5.932(1) angstrom] with stoichiometric composition and an enhanced dislocation density (8 approximate to 1011 cm-2). The latter parameter leads to an increase of the electrical resistivity in the high-temperature regime, as well as to the appearance of phonon resonance with a characteristic frequency coPR = 3.8(1) THz. Being in the same range (i.e., 3-5.5 THz) with the sulfur optical modes of highest group velocities, it results in a drastic reduction (by similar to 75%) of thermal conductivity (K) at lower temperatures (i.e., < 100 K), as well as in the appearance of a characteristic minimum in K at T approximate to 30 K. Furthermore, the studied galena is characterized by phonon-drag behavior and by temperature dependent switch of the charge carrier scattering mechanism regime (i.e., scattering on dislocations for T < 100 K, on acoustic phonons for 100 K < T < 170 K and on both acoustic and optical phonons for 170 K < T < 300 K). The combined theoretical calculation and optical spectroscopic study confirm this mineral to be a direct gap degenerate semiconductor. The possible origins of the second-order Raman spectrum are discussed.

The structural and physical properties of Y5Ir6Sn18 grown from Sn-flux as large single crystals are studied. Y5Ir6Sn18 crystallizes with a unique structure [space group Fm3̄m, a = 13.7706(1) Å], which is characterized by a strong disorder. A transmission electron microscopy (TEM) study indicated that the structural model of Y5Ir6Sn18 obtained from X-ray diffraction methods is an average description of a complex intergrowth of domains with different structural arrangements. The studied stannide is a type-II superconductor with a critical temperature Tc = 2.1 K, a rather weak electron-phonon coupling and conventional s-wave BCS-like mechanisms. Performed theoretical electronic band structure calculations indicated the inconsistency of an idealized structural model earlier reported for Y5Ir6Sn18.

The isothermal section of the Er–Zr–Ni phase diagram in the Er–Zr–ErNi region at 870 K has been studied by means of X-ray phase and structural analyzes and energy-dispersive X-ray spectroscopy. The mutual solubility of the components Er, Zr and Ni at 800 ° С was established: Zr dissolves up to 3 at. % Er and practically does not dissolve Ni; Ni practically does not dissolve Er and Zr; Er dissolves up to 12 at. % Zr and practically does not dissolve Ni. The following solid solutions of substitution were detected: Er 3- x Zr x Ni (0≤ x ≤0.24; structure type (ST) Fe 3 C, space group (SG) Pnma, a = 6.804–6.801(1) Ǻ, b = 9.430–9.431(3) Ǻ, c = 6.245–6.241(2) Ǻ); Er 3- x Zr x Ni 2 (0≤ x ≤0.04; ST Er 3 Ni 2 , SG R , a = 8.472–8.451(2) Ǻ, c = 15.680–15.665(4) Ǻ). Two ternary compound with the narrow homogeneity range Er x Zr 1- x Ni 2 (0.12≤ х ≤ 0.24) and Er 1+ x Zr 1− x Ni (0.33 ≤ x ≤ 0.48) occurs in the system. The Er x Zr 1- x Ni 2 (0.12 ≤ х ≤ 0.24) compound crystallizes in the cubic MgCu 2 type of structure, а = 6.959(6)–6.987(5) Å). The crystal structure of Er 1+ x Zr 1− x Ni (0.33≤ x ≤ 0.48) compound was investigated by means of EDX and powder X-ray diffraction. It crystallizes in the TiNiSi ST (SG Pnma , No. 62, oP 12, а = 6.8175(7)–6.8253(8) Å, b = 4.6494(5)–4.6575(6) Å, c = 8.1021(9)–8.113(1) Å). In Er 1+x Zr 1−x Ni, the Er/Zr statistical mixture leading to nonequiatomic compositions occupies the position corresponding to the nickel site of the TiNiSi structure type. The isostructural rare earth compounds R 1+x Zr 1−x Ni (0.33≤ x ≤ 0.48; R=Tm, Lu) have been synthesized and their homogeneity ranges were refined. Keywords: ternary system, phase equilibria, intermetallic compounds, crystal structure.

Crystal structures of U(3)Rh4Ge(13) [structure type HT-Y3Pt4Ge13, space group R3c, a = 5.6004(6) A, c = 15.5158(1) A, R-B = 0.022, R-p = 0.021] and of Th2Rh3Ge5 [structure type U2Co3Si5, space group Ibam, a = 10.0572(1) A, b = 11.9142(1) A, c = 6.0997(1) A, RB = 0.027, R-P = 0.037] are refined by powder X-ray diffraction method. Their structural relationships with primitive cubic Yb3Rh4Sn13 and body-centered tetragonal ThCr2Si2 types, respectively are discussed. The ac and dc magnetic susceptibility measurements on U3Rh4Ge13 revealed an antiferromagnetic ordering at TN = 22 K followed by a metamagnetic transition below 5 K. The magnetic entropy S-mag approximate to Rln4 at T-N indicates U3Rh4Ge13 to follow the classical LS coupling scheme. This finding together with the performed theoretical DFT calculations hint toward localized nature of 5f states in the studied germanide. U3Rh4Ge13 reveals metallic transport properties, low thermal conductivity (i.e. 0.4-0.6 W m(-1) K-1) as well as displays a structural phase transition in the temperature range of 292-315 K. Electrical resistivity measurements and theoretical DFT calculations indicated Th2Rh3Ge5 to be a simple metal. (c) 2022 Elsevier B.V. All rights reserved.

Polymorphism is observed in the Y3+xRh4Ge13-x series. The decrease of Y-content leads to the transformation of the primitive cubic Y3.6Rh4Ge12.4 [x = 0.6, space group Pm3̄n, a = 8.96095(9) Å], revealing a strongly disordered structure of the Yb3Rh4Sn13 Remeika prototype, into a body-centred cubic structure [La3Rh4Sn13 structure type, space group I4132, a = 17.90876(6) Å] for x = 0.4 and further into a tetragonal arrangement (Lu3Ir4Ge13 structure type, space group I41/amd, a = 17.86453(4) Å, a = 17.91076(6) Å) for the stoichiometric (i.e. x = 0) Y3Rh4Ge13. Analogous symmetry lowering is found within the Y3+xIr4Ge13-x series, where the compound with Y-content x = 0.6 is crystallizing with La3Rh4Sn13 structure type [a = 17.90833(8) Å] and the stoichiometric Y3Ir4Ge13 is isostructural with the Rh-analogue [a = 17.89411(9) Å, a = 17.9353(1) Å]. The structural relationships of these derivatives of the Remeika prototype are discussed. Compounds from the Y3+xRh4Ge13-x series are found to be weakly-coupled BCS-like superconductors with Tc = 1.25, 0.43 and 0.6, for x = 0.6, 0.4 and 0, respectively. They also reveal low thermal conductivity (<1.5 W K-1 m-1 in the temperature range 1.8-350 K) and small Seebeck coefficients. The latter are common for metallic systems. Y3Rh4Ge13 undergoes a first-order phase transition at Tf = 177 K, with signatures compatible to a charge density wave scenario. The electronic structure calculations confirm the instability of the idealized Yb3Rh4Sn13-like structural arrangements for Y3Rh4Ge13 and Y3Ir4Ge13.

Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P4̄3n(α,0,0)000(0,α,0)000(0,0,α)000; a = 8.72328(1) Å, α = 0.4974(2)] modulated crystal structure. A slight shift of the composition towards higher Yb-content (i.e. Yb3.2Co4Ge12.8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pm3̄n, a = 8.74072(2) Å] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature-dependent intermediate valence state varying from +2.60 to +2.66 for the temperature range 85-293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements.

A series of new ternary isostructural R4Co2C3 (R = Y, Gd, Tb) carbides was synthesized by annealing of arc-melted stoichiometric samples. The crystal structure of Tb4Co2C3 [space group P2/m, Pearson symbol mP18, a = 12.754(2) Å, b = 3.6251(4) Å, c = 7.0731(9) Å, β = 105.601(6)°] was solved by direct methods from neutron powder diffraction data collected at 100 K. The room temperature unit cell parameters of the new phases were determined by X-ray powder diffraction technique. The crystal structure of Tb4Co2C3 is characterized as an intergrowth structure resulting from the stacking of alternating TbCoC (YCoC-type) and Tb2C (anti-CdCl2 type) fragments with a 2 : 1 ratio. Tb4Co2C3 orders ferromagnetically at TC = 35(1) K, whereas the isostructural Gd4Co2C3 reveals two magnetic transitions at TC1 = 82(3) K and TC2 = 13(2) K. Density functional theory (DFT) calculations confirm that the magnetic moments of the R4Co2C3 (R = Gd, Tb) carbides are exclusively due to the rare-earth elements. Y4Co2C3 is shown to be a Pauli-paramagnet by experimental and theoretical studies.

The isothermal section of the Er–Zr–Ni phase diagram in the ErNi–Zr–Ni region at 800 °С has been studied by means of X-ray phase and structural analyzes and energy-dispersive X-ray spectroscopy. The mutual solubility of the components Er, Zr and Ni at 800 ° С is insignificant: Zr dissolves up to 3 at. % Er and practically does not dissolve Ni; Ni practically does not dissolve Er and Zr; Er dissolves up to 13 at. % Zr and practically does not dissolve Ni. The existence of the binary compounds Er 2 Ni 17 , ErNi 5 , ErNi 4 , α -Er 2 Ni 7 , ErNi 3 , Er 0,98 Ni 2 , ErNi, ZrNi 5 , Zr 2 Ni 7 , ZrNi 3 , Zr 8 Ni 21 , Zr 7 Ni 10 , ZrNi and Zr 2 Ni has been confirmed in ErNi–Zr–Ni region. The following solid solutions of substitution based on the binary Er–Ni and Zr–Ni compounds were detected: Er 2- x Zr x Ni 17 (0≤ x ≤0,16; str. type Th 2 Ni 17 ); Er 1- x Zr x Ni 5 (0≤ x ≤0,63; str. type CaCu 5 ); Er 1- x Zr x Ni 4 (0≤ x ≤0,30; str. type PuNi 4 ); α –Er 2– x Zr x Ni 7 (0≤ x ≤0,05; str. type Er 2 Co 7 ); Er 1- x Zr x Ni 3 (0≤ x ≤0,18; str. type PuNi 3 ); Er 0,98- x Zr x Ni 2 (0≤ x ≤0,34; str. type TmNi 2 ); Er 1- x Zr x Ni (0≤ x ≤0,5; str. type), Zr 1- x Er x Ni 5 (0≤ x ≤0,30; str. type AuBe 5 ); Zr 2- x Er x Ni 7 (0≤ x ≤0,14; str. type Zr 2 Ni 7 ); Zr 7- x Er x Ni 10 (0≤ x ≤0,18; str. type Zr 7 Ni 10 ); Zr 1- x Er x Ni (0≤ x ≤0,32; str. type CrB); та Zr 2- x Er x Ni (0≤ x ≤0,30; str. type Al 2 Cu). Other binary compounds don’t dissolve any significant amount of the third component. One ternary compound Er x Zr 1- x Ni 2 (0,12≤ х ≤0,24) with the narrow homogeneity range at 800 o C occurs in the system. It crystallizes in the cubic MgCu 2 type of structure. It’s crystal structure has been refined for Er 0 , 17 Zr 0 , 83 Ni 2 composition using powder X-ray diffraction data: MgCu 2 str. type, Fd- 3 m space group, Z = 8, а = 6,987 (5) Å, R І =0,0915 for 8 independent reflections, І о > 2σ (І о ). The ternary compound Er x Zr 1- x Ni 2 (0,12 ≤ х ≤ 0,24) coexists with the solid solution Er 0,98- x Zr x Ni 2 (0 ≤ x ≤ 9,5) (СТ TmNi 2 ). The morphotropic row of cubic Laves phases MgCu 2 → TmNi 2 – a defect superstructure of the MgCu 2 type with doubled a -lattice parameter has been defined along the pseudo-binary “ZrNi 2 ”–Er 0 . 9 8 Ni 2 cross section. Keywords: ternary system, phase equilibria, intermetallic compounds, crystal structure.

Co61Ta6B33, Co59Ta8B33, Co57Ta10B33 and Co53Ta10B37 bulk metallic glasses (BMGs) exhibit a good combination of the ultra-high fracture strength in the range of about 5.4-6.2 GPa, Vickers hardness of 1459-1653 HV0.2 and plastic strain of 0.3-3.2%, depending on composition. Glass forming-ability and physical properties of Co-Ta-B BMGs are discussed in relationship to the Ta and B content and atomic structure. Crystallization upon isochronal and isothermal annealing is studied using differential scanning calorimetry and X-ray diffraction. A novel crystalline phase with similar to Ta2Co15B8 or similar to TaCo7B4 formula is shown to form upon glass annealing. The incubation time for isothermal crystallization in the supercooled liquid state near T-g is supposed to be sufficient for thermoplastic forming of Co-Ta-B BMGs. (C) 2020 Elsevier B.V. All rights reserved.

A new series of isostructural rare earth compounds R1+xZr1-xNi (R = Er, Tm, Lu; x similar to 0.5) was synthesized from the elements by arc melting and subsequent annealing at 870 K for 1400 h. The crystal structures of the intermetallic compounds were investigated by means of single-crystal X-ray diffraction. They all crystallize in the TiNiSi structure type (space group Pnma, No. 62, oP12). In R1+xZr1-xNi, the R/Zr statistical mixture leading to nonequiatomic compositions occupies the position corresponding to the nickel site of the TiNiSi structure type. The calculated shortest interatomic distances are close to the sums of the single-bond covalent radii of respective elements. Electronic structure calculations performed with the tight-binding LMTO method revealed the nonzero density of states at the Fermi level and suggest metallic character. R1+xZr1-xNi (R = Er, Tm, Lu; x similar to 0.5) undergoes no long-range magnetic ordering down to 2 K.

Abstract The crystal structure of Sc3Ir4Si13+x (x = 0.22) [space group Pm3‾n$Pm‾{3}n$, a = 8.4651(1) Å] is found to be a new disordered variant of the primitive cubic Yb3Rh4Sn13 Remeika prototype. The silicide is stable in the narrow temperature range of 1283–1397 °C and reveals metallic properties. The crystal structure of Sc4Ir7Ge6 [U4Re7Si6 type, space group Im3‾m$Im‾{3}m$, a = 8.1397(8) Å] is refined for the first time. The electronic band structure calculations reveal that the properties of this germanide can be explained based on the free electron gas model. Both compounds reveal close structural relationships to the simple perovskite structure.

Two new quaternary selenides of the alpha-TlSe structure type have been synthesized and characterized. Single crystal X-ray diffraction analysis has revealed that Tl2Ga2SnSe6 crystallizes with space group I4/mmc, a =8.095(1), c=6.402(1) angstrom, with a refined composition of Tl1-xGa1-ySny Se-2 (x= y=0.345(5)), Z=4, R1=0.028; wR2= 0.066. The crystal structure of the isostructural compound Tl2Ga2GeSe6 has been determined by means of powder X-ray diffraction: space group I4/mmc, Z= 4, a= 8.0770(4 ), c= 6.2572(5) angstrom, refined composition Tl1-xGa1-ySny Se-2, x=0343(5), y=0.35(2), (R-B(I) = 0.084; R-p = 0.041; R-PW= 0.058). According to their optical absorption spectra all compounds are semiconductors with relatively narrow direct band gaps of 2.15(3) and 2.05(5) eV for the Ge and Sn phase, respectively.