First-order antiferromagnetic ordering and metamagnetic transition in (TbPd3)(8)T (T=Ga and Ge)

(TbPd3)(8)T (T=Ga and Ge) compounds have the cubic, Pm3m symmetry and are a superstructure derivative of the cubic, AuCu3-type, TbPd3. The ternary com pounds order antiferromagnetically and the Neel temperature is different fr om the binary compound TbPd3, which has an antiferromagnetic ordering at 3 K. Two transitions are observed in (TbPd3)(8)Ge, one at 4 K and the other a t 5.2 K. The compound (TbPd3)(8)Ga has an antiferromagnetic ordering at 5.2 K. The resistivity exhibits hysteresis in the transition regime in both co mpounds. The magnetic transitions are first-order like and sharp metamagnet ic transition is observed below the magnetic ordering temperature in both ( TbPd3)(8)Ga and (TbPd3)(8)Ge. (C) 2000 American Institute of Physics. [S002 1-8979(00)31008-8].