Magnetic properties and structural phase transition of CePd2Ga2 with CaBe2Ge2-type structure

By measuring the magnetic susceptibility the specific heat and the electric al resistivity, we have investigated the low-temperature properties of new compounds CePd2Ga2 and LaPd2Ga2 with the tetragonal CaBe2Ge2-type structure . The former compound shows antiferromagnetic ordering at 2.3 K and a struc tural phase transition into a triclinic structure at 125 K, and the latter is superconducting below 1.9 K and shows a similar structural transition at 62 K. From the analysis of published data, it is proposed that the c/a rat io may be a decisive parameter for the structural instability in CaBe2Ge2-t ype compounds.