In typical rare-earth lanthanide compounds, the localized 4 f electrons have a weak effect on the electrical conduction, limiting their influence on the Berry curvature and, hence, the intrinsic anomalous Hall effect. A comprehensive study of the magnetic, thermodynamic, and transport properties of single-crystalline NdGaSi, guided by first-principles calculations, reveals a ferromagnetic ground state that induces a splitting of quasiflat 4 f electronic bands and positions them near the Fermi energy. The observation of an extraordinarily large intrinsic anomalous Hall conductivity of 1165 Q-1 cm-1 implies the direct involvement of localized states in the generation of nontrivial band crossings around the Fermi energy. The angle-resolved photoemission spectroscopy measurements provide direct evidence of nontrivial crossing of the 4 f bands with dispersive bands. These results are remarkable when compared to ferrimagnetic NdAlSi, which differs only in a nonmagnetic atom (a change in the principal quantum number n of the outer p orbital) with the same number of valence electrons and does not exhibit any measurable anomalous Hall conductivity.

We report a comprehensive investigation of the physical properties of single crystals of Dirac semimetal EuAuBi, using neutron diffraction, magnetization, electrical transport, and specific heat measurements. EuAuBi crystallizes in a hexagonal structure with space group P63mc (no. 186). First-principles calculations using density functional theory characterize it as a Dirac semimetal, with a notable band crossing in proximity to the Fermi level (EF) along the P-A direction. The crystal exhibits three distinct magnetic phases at 4 K (TN1), 3.5 K (TN2), and 2.8 K (TN3) as observed from magnetic and specific heat measurements. However, zero-field neutron diffraction resolves only two magnetic phases: a commensurate antiferromagnetic phase and a canted antiferromagnetic phase. Field-dependent ac and dc magnetization measurements uncover field-induced nontrivial spin textures in the magnetic field range 1.5 to 3 T, manifested as a tilted plateau in the magnetization curves. The interplay between conduction carriers and these spin textures is further evidenced by unique features in the magnetic field-dependent longitudinal resistivity. Finally, we present a comprehensive magnetic phase diagram of EuAuBi, highlighting diverse spin alignments present in the material. EuAuBi thus emerges as a rare material system in which both momentum-space and real-space Berry curvature effects may coexist, providing a unique opportunity to investigate their interplay.

LaCrGe3 has become a playground to understand quantum critical phenomena in ferromagnetic (FM) materials. It has also garnered attention due to its peculiar two FM phases. Here, we demonstrate the presence of these phases using the Hall effect. Continuous temperature-dependent Hall resistivity measurements at fixed magnetic fields clearly demonstrate the presence of these phases, regardless of the direction of the applied magnetic field. The remanent Hall resistivity and Hall coefficient undergo a maximum and a minimum, respectively, at the boundary between the two phases. We observe significantly large anomalous Hall conductivity of 1160 ohm-1cm-1 at 2 K when the magnetic field is applied along the magnetic easy axis, which is dominated by intrinsic effects, at least in the low-temperature FM phase. In the paramagnetic (PM) phase, hexagonal LaCrGe3 exhibits opposite charge carrier polarities along different crystallographic directions, attributed to the anisotropic Fermi surface geometry, a phenomenon known as "goniopolarity". The coexistence of goniopolar transport and unconventional magnetic phases may lead this material as a promising candidate for future electronic devices.

Magnetic kagome metals provide a fertile platform for exploring unusual magnetotransport phenomena arising from the intricate interplay between electronic topology, electron correlations, and magnetic order. MgMn6Sn6 is a room-temperature kagome ferromagnet with strong in-plane magnetic anisotropy. Here, we report a combined study of single-crystal neutron diffraction (SCND) and magnetotransport properties of MgMn6Sn6, supported by first-principles calculations. Our SCND measurements reveal a non-collinear arrangement of Mn magnetic moments within the basal plane of the kagome bilayer. The Hall conductivity shows a substantial intrinsic contribution of approximately 0.29 e^2/h per kagome layer, which is nearly isotropic with respect to the field orientation. At low temperatures, the anomalous Hall conductivity develops a pronounced anisotropic extrinsic component, highlighting the directional sensitivity of scattering processes. The significantly large value of the Sommerfeld coefficient, in the absence of f-electrons, underscores enhanced electron correlation. Therefore, the non-collinear kagome ferromagnet MgMn6Sn6 is a promising candidate for studying the effects of electron correlation on magnetotransport properties.

Topological magnets with nontrivial spin texture have attracted considerable interest because they display a rich spectrum of emergent quantum phenomena. Here, we present a combined experimental and theoretical investigation of the magnetic and magnetotransport properties of EuAuAs, an antiferromagnet with Néel temperature (T_N) ∼ 6 K. The temperature and magnetic field dependence of electrical resistivity and magnetization demonstrate that the charge transport in EuAuAs is strongly influenced by the spin configuration of local Eu moments. Below T_N, both longitudinal magnetoresistance (LMR) and transverse magnetoresistance (TMR) are positive at low fields but large and negative at high fields. With increasing temperature, TMR becomes positive above 60 K, whereas LMR remains negative up to 100 K. The low-field positive LMR and TMR originate from weak antilocalization (WAL). The WAL contribution in TMR is well captured by the Hikami-Larkin-Nagaoka model, whereas the LMR data are described by a generalized Altshuler-Aronov framework. Moreover, we observe a giant topological Hall effect arising from the scalar spin chirality, which is further supported by the helical magnetic structure obtained from the ab-initio calculations. The observed anisotropy in longitudinal resistivity and magnetoresistance underscores the very nature of the Fermi surface of the EuAuAs, as confirmed by first-principles calculations. These results establish EuAuAs as a unique platform for exploring the interplay between electronic structure and noncoplanar spin texture in a centrosymmetric helical magnet.

We explore the intriguing topological itinerant magnet MgMn_6Sn_6, characterized by bilayer kagome Mn layers encasing a hexagonal Sn layer. Using ab initio Density functional theory and Dynamical mean-field theory calculations, we uncover the complex electronic properties and many-body configuration of its magnetic ground state. Mn d-orbital electrons form a frustrated many-body ground state with significant quantum fluctuations, resulting in competing antiferromagnetic and ferromagnetic spin exchanges. Our band dispersion calculations reveal a mirror symmetry-protected nodal line in the k_z = 0 plane. When spin-orbit coupling (SOC) is introduced, the gap is formed along the nodal line lifted due to broken time-reversal symmetry with magnetic ordering, leading to substantial intrinsic Berry curvature. We identify Dirac fermions, van Hove singularities, and flat band near the Fermi energy (E_F), with SOC introducing a finite gap at key points. The unique proximity of the flat band to E_F suggests potential instabilities. Spin-orbit coupling opens a 20 meV gap at the quadratic touching point between the Dirac and flat band, bestowing a nonzero Z_2 invariant. This leads to a significant spin Hall conductivity. Despite the presence of large incoherent scattering due to electronic interactions, band crossings and flat band features persist at finite temperatures. MgMn_6Sn_6 exhibits intriguing topological and magnetic properties, with promising applications in spintronics.

The interplay between charge density wave (CDW) formation and electron correlations can lead to the emergence of novel topological phases in materials. In quasi‐2D 1T‐TaS 2 , below approximately 150 K, the system transitions from a nearly commensurate (NC) to a commensurate (C) CDW phase. Here, it is shown that the NC‐CDW to C‐CDW phase transition is marked by the emergence of a finite planar Hall and nonlinear Hall effect, alongside sign changes in the ordinary Hall and thermoelectric signals, indicating the reconstruction of the Fermi surface in the C‐CDW phase. The theoretical calculations suggest that the C‐CDW phase, stabilized by specific layer stacking, breaks both mirror and inversion symmetries. This leads to finite Berry curvature and a substantial Berry curvature dipole, giving rise to the observed planar Hall and nonlinear Hall effect. This study highlights the nontrivial band geometry‐driven physics of 1T‐TaS 2 and opens new possibilities for developing innovative sensors.

Trigonal Cr5Te8, a self-intercalated van der Waals ferromagnet with an out-of-plane magnetic anisotropy, has long been known to crystallize in a centrosymmetric structure. However, optical second harmonic generation experiments, together with comprehensive structural analysis, indicate that this compound rather adopts a non-centrosymmetric structure. Lorentz transmission electron microscopy reveals the presence of Néel-type skyrmions, consistent with its non-centrosymmetric structure. A large anomalous Hall conductivity of 102 ohm^-1cm^-1 at low temperature stems from intrinsic origin, which is larger than any previously reported values in the bulk Cr-Te system. Notably, spontaneous topological Hall resistivity arising from the skyrmionic phase has been observed. Our findings not only elucidate the unique magnetic and magneto-transport properties of non-centrosymmetric trigonal Cr5Te8, but also open new avenues for investigating the effects of broken inversion symmetry on material properties and their potential applications.

Recent magnetotransport studies on uniaxial ferromagnets have reported a cusp-like feature in Hall resistivity when the magnetic field is tilted away from the conventional orthogonal direction of the Hall measurement. This feature has often been attributed to the topological Hall effect arising from a non-coplanar spin structure. In this Letter, we have studied the uniaxial ferromagnet SmMn$_2$Ge$_2$ to demonstrate that this feature is rather a consequence of the non-orthogonal geometry of the Hall measurement and is expected to appear whenever the magnetic field is applied away from the easy axis of magnetization, non-orthogonal to the sample plane. The Hall resistivity, exhibiting this feature, scales with the orthogonal component of the magnetization, indicating that the observed feature is simply a manifestation of the anomalous Hall effect. We explain the origin of this feature based on the evolution of ferromagnetic domains under a non-orthogonal external magnetic field.

We report the single‐crystal growth and physical properties of SmGaSi, a member of the rare‐earth gallium‐silicide family. The system adopts the centrosymmetric I 4 1 / amd ‐type structure, with Ga and Si sharing the same crystallographic site in equal proportion. Magnetization measurements reveal antiferromagnetic order at T N = 11 K, followed by a subtle spin‐reorientation transition around 7.8 K, and a small anisotropy between the [100] and [001] axes. Electrical resistivity shows metallic behavior down to 2 K with a low residual resistivity ratio of 1.9, indicative of site‐disorder scattering. Transverse magnetoresistance exhibits an unusual cusp‐like field dependence, deviating from classical B 2 scaling, attributed to weak antilocalization arising from strong spin–orbit coupling, and could indicate nontrivial Berry curvature effects. By fitting the magnetoconductance to a modified Hikami–Larkin–Nagaoka model, we extract an effective coherence length of 22 nm at 2 K and an anomalously large channel‐count parameter, consistent with multiple 3D conduction pathways. The phase coherence length diminishes with increasing temperature following combined electron–electron and electron–phonon scattering. Our results establish SmGaSi as an antiferromagnet exhibiting spin–orbit–driven quantum interference, positioning it as a promising platform for exploring such physics in rare‐earth intermetallics and opening new pathways to investigate the largely unexplored ternary rare‐earth gallides.

CrSb has recently gained immense attention as an altermagnetic candidate. This work reports on the experimental observation of direction-dependent conduction polarity (DDCP) in altermagnetic CrSb through Hall and Seebeck thermopower measurements. Conduction is dominated by holes along the c $c$ -axis and by electrons in the ab $\textit{ab}$ -plane of the hexagonal crystal of CrSb. Density functional theory (DFT) calculations indicate that DDCP in CrSb arises from a multicarrier mechanism, where electrons and holes living in distinct bands dominate conduction along different crystallographic directions. Furthermore, DFT predicts that DDCP exists within a narrow energy window near the Fermi level and is sensitive to small doping levels. This prediction is experimentally validated by the loss of DDCP in hole-doped Cr0.98V0.02Sb. These findings highlight the potential for tunable electronic behavior in CrSb, offering promising avenues for applications in devices that require both p-type and n-type functionalities within a single material.

MgMn _6 Sn _6 is the itinerant ferromagnet on the kagome lattice with high ordering temperature featuring complex electronic properties due to the nontrivial topological electronic band structure where the spin–orbit coupling (SOC) plays a crucial role. Here, we report a detailed ferromagnetic resonance (FMR) spectroscopic study of MgMn _6 Sn _6 aimed to elucidate and quantify the intrinsic magnetocrystalline anisotropy that is responsible for the alignment of the Mn magnetic moments in the kagome plane. By analyzing the frequency, magnetic field, and temperature dependences of the FMR modes, we have quantified the magnetocrystalline anisotropy energy density that reaches the value of approximately 3.5· 10^6 erg/cm ^3 at T = 3 K and reduces to about 1· 10^6 erg/cm ^3 at T = 300 K. The revealed significantly strong magnetic anisotropy suggests a sizable contribution of the orbital magnetic moment to the spin magnetic moment of Mn, supporting the scenario of the essential role of SOC for the nontrivial electronic properties of MgMn _6 Sn _6 .

Topological states of matter exhibit unique protection against scattering by disorder. Different topological classes exhibit distinct forms and degrees of protection. Here, we investigate the response of the ferromagnetic nodal line semimetal Fe$_3$GeTe$_2$ to disorder and electronic interactions. By combining global magneto-transport with atomic-scale scanning tunneling spectroscopy we find a simultaneous onset of diverse phenomena below a common temperature scale of about 15 K: A crossover from metallic to insulating temperature dependence of the longitudinal resistivity, saturation of the anomalous Hall conductivity to its maximal value, formation of a sharp zero-bias dip in the tunneling density of state, and emergence of multi-fractal structure of the electronic wavefunction peaking at the Fermi energy. These concurrent observations reflect the emergence of a novel energy scale possibly related to the opening of a gap in the nodal line band of Fe$_3$GeTe$_2$. Our study provides overarching insight into the role of disorder, electronic interactions and Berry curvature in setting the micro- and macro-scale responses of topological semimetals.

Recent magnetotransport studies on uniaxial ferromagnets have reported a cusplike feature in Hall resistivity when the magnetic field is tilted away from the conventional orthogonal direction of the Hall measurement. This feature has often been attributed to the topological Hall effect arising from a non-coplanar spin structure. In this article, we have studied the uniaxial ferromagnet SmMn_2Ge_2 to demonstrate that this feature is rather a consequence of the nonorthogonal geometry of the Hall measurement and is expected to appear whenever the magnetic field is applied away from the easy axis of magnetization, nonorthogonal to the sample plane. The Hall resistivity, exhibiting this feature, scales with the orthogonal component of the magnetization, indicating that the observed feature is simply a manifestation of the anomalous Hall effect. We explain the origin of this feature based on the evolution of ferromagnetic domains under a nonorthogonal external magnetic field.

Berry curvature physics is responsible for the anomalous electromagnetic responses in solids. One such response is the circular photogalvanic effect (CPGE), typically observed in systems with pronounced Berry curvature─such as flat-band systems or topological semimetals featuring band crossings near the Fermi level, where Berry curvature exhibits sharp discontinuities. To maximize CPGE, one must develop the ability to tune their electronic band dispersion without introducing disorder, which is a challenging endeavor. Here, we demonstrate that it is possible to maximize the CPGE response in a topological material by a fundamentally different approach: controlling the proximity of a given system to a symmetry-breaking phase transition that induces a reconstruction of the electronic band structure. Through measurements of the longitudinal circular photogalvanic effect in the Weyl semimetal (TaSe4)2I, we show that the circular photogalvanic effect can be amplified by a dramatic factor of 2 by tuning the proximity of this compound to charge density wave order. The first-principles calculations we present here show that this enhancement arises from the development of the CDW order parameter and the divergence of the associated relaxation time near the critical temperature. Therefore, this work provides a paradigm for boosting CPGE responses in solids─not by engineering band structure alone but by exploiting critical fluctuations near phase transitions in topological materials.

The solid-solution alloys of Mn-Zn-Ga and Mn-Zn-Sn have been synthesized by a high-temperature method and structurally characterized by X-ray diffraction studies. The substitutional solid-solution alloys that crystallize in the chiral space group P4132 or P4332 adopt the A13-type structure (β-Mn). Similar to β-Mn, the 20 atoms in the cubic unit cell are distributed over 8c and 12d Wyckoff positions. In the structure of β-Mn-type Mn-Zn-Ga (Sn) alloys, the 8c position is occupied by the Mn atom only and remains unaffected by chemical substitution. The 12d site that forms a hyperkagomé network ("distorted windmill") composed of corner-sharing triangles is randomly occupied by Mn, Zn, and M (M = Ga or Sn) atoms in the alloys of Mn0.80Zn0.15Ga0.05 and Mn0.80Zn0.15Sn0.05. Both of them possess a magnetically frustrated ground state, and the magnetic frustration is attributed to the formation of a distorted network of corner-sharing triangles composed of mixed Mn/Zn/Ga(Sn) sites. The negative temperature coefficient of resistivity in Mn0.80Zn0.15Sn0.05 obeys the Mooij criterion, and the very low mobility of charge carriers can be attributed to the high degree of atomic disorder within the structures.

At ambient pressure, HfTe_5 is a material at the boundary between a weak and a strong topological phase, which can be tuned by changes in its crystalline structure or by the application of high magnetic fields. It exhibits a Lifshitz transition upon cooling, and three-dimensional (3D) quantum Hall effect (QHE) plateaus can be observed at low temperatures. Here, we have investigated the electrical transport properties of HfTe_5 under hydrostatic pressure up to 3 GPa. We find a pressure-induced crossover from a semimetallic phase at low pressures to an insulating phase at about 1.5 GPa. Our data suggest the presence of a pressure-induced Lifshitz transition at low temperatures within the insulating phase around 2 GPa. The quasi-3D QHE is confined to the low-pressure region in the semimetallic phase. This reveals the importance of the semimetallic groundstate for the emergence of the QHE in HfTe_5 and thus favors a scenario based on a low carrier density metal in the quantum limit for the observed signatures of the quasi-quantized 3D QHE.

The interplay between magnetism and strong electron correlation in magnetic materials discerns a variety of intriguing topological features. Here, we report a systematic investigation of the magnetic, thermodynamic, and electrical transport properties in NdGaSi single crystals. The magnetic measurements reveal a magnetic ordering below T_N (11 K), with spins aligning antiferromagnetically in-plane, and it orders ferromagnetically (FM) out-of-plane. The longitudinal resistivity data and heat capacity exhibit a significant anomaly as a consequence of the magnetic ordering at TN. The magnetoresistance study shows significantly different behavior when measured along either direction, resulting from the complex nature of the magnetic structure, stemming from complete saturation of moments in one direction and subsequent spin flop transitions in the other. Remarkably, we have also noticed an unusual anisotropic anomalous Hall response. We have observed a giant anomalous Hall conductivity (AHC) of 1730 ohm-1 cm-1 and 490 ohm-1 cm-1 at 2 K, with B // [001] and B // [100], respectively. Our scaling analysis of AHC reveals that the anomalous Hall effect in the studied compound is dominated by the Berry phase-driven intrinsic mechanism. These astonishing findings in NdGaSi open up new possibilities for antiferromagnetic spintronics in rare-earth-based intermetallic compounds.

Compounds with a kagome lattice exhibit intriguing properties and the charge density wave (CDW) adds an additional layer of interest to research on them. In this study, we investigate the temperature and magnetic field dependent electrical properties under a chemical substitution and hydrostatic pressure of ScV6Sn6, a non-magnetic charge density wave (CDW) compound. Substituting 5 % Cr at the V site or applying 1.5 GPa of pressure shifts the CDW to 50 K from 92 K. This shift is attributed to the movement of the imaginary phonon band, as revealed by the phonon dispersion relation. The longitudinal and Hall resistivities respond differently under these stimuli. The magnetoresistance (MR) maintains its quasilinear behavior under pressure, but it becomes quadratic after Cr substitution. The anomalous Hall-like behavior of the parent compound persists up to the respective CDW transition under pressure, after which it sharply declines. In contrast, the longitudinal and Hall resistivities of Cr substituted compounds follow a two-band model and originates from the multi carrier effect. These results clearly highlight the role of phonon contributions in the CDW transition and call for further investigation into the origin of the anomalous Hall-like behavior in the parent compound.