Crystal structure and physical properties of new Ca2TGe3 (T = Pd and Pt) germanides

The crystallographic, electronic transport and thermal properties of Ca2PdGe3 and Ca2PtGe3 are reported. The compounds crystalize in an ordered variant of the AlB2 crystal structure, in space group P6/mmm, with the lattice parameters a = 8.4876(4) Å/8.4503(5) Å and c = 4.1911(3) Å/4.2302(3) Å for Ca2PdGe3 and Ca2PtGe3, respectively. The resistivity data exhibit metallic behavior with residual-resistivity-ratios (RRR) of 13 for Ca2PdGe3 and 6.5 for Ca2PtGe3. No superconducting transition is observed down to 0.4K. Specific heat studies reveal similar values of the Debye temperatures and Sommerfeld coefficients: ΘD = 298K, γ = 4.1mJmol−1K−2 and ΘD = 305K, γ = 3.2mJmol−1K−2 for Ca2PdGe3 and Ca2PtGe3, respectively. The low value of γ is in agreement with the electronic structure calculations.