Ternary Laves phases with the MgCu4Sn-type structure: RECo4Mg (RE = Gd, Dy-Tm, Lu), EuNi4Mg and RET4Cd (RE = Y, La-Nd, Sm, Gd-Dy; T = Cu, Pt)

Twenty five new ternary Laves phases RET4Mg and RET4Cd (RE = rare earth element; T = Co, Ni, Cu, Pt) have been synthesized from the elements using niobium or tantalum tubes as inert crucible materials. The lattice parameters have been derived frompowder X-ray diffraction data. The structures of Ce-1.41( 1)Co4Mg0.59(1), Dy-1.10( 1)Co4Mg0.90(1), LaPt4Cd, Y-1.10( 1)Cu4Cd0.90(1), Ca-0.93( 1)Cd-0.07( 1)Pd-2 and Eu-0.87( 2)Cd-0.13( 2)Pd-2 were refined from single-crystal X-ray diffractometer data. Most phases show certain degrees of RE/Mg or RE/Cd disorder. The quenched phases are assigned to the MgCu2 structure, while the annealed ones adopt the MgCu4Sn type, a translationengleiche superstructure variant of the aristotype. The annealing time has a substantial influence on the degree of ordering and is expressed in the lattice parameters, i.e. larger ones for the disordered samples. The REPt4Cd (RE = La-Nd) samples have been characterized with respect to their magnetic properties. LaPt4Cd is a diamagnet, while CePt4Cd (2.23(1) mu(B)), PrPt4Cd (3.40(1) mu(B)) and NdPt4Cd (3.43(1) mu(B)) are Curie-Weiss paramagnets. The cerium compound shows a slight moment reduction. NdPt4Cd is ordered ferromagnetically at T-C = 4.4(1) K.