Synthesis and structures of samarium platinum germanides : SmPtGe2 and Sm2Pt3Ge5

We performed single-crystal structure analysis of two ternary samarium platinum germanides SmPtGe2 and Sm2Pt3Ge5. SmPtGe2 crystallizes in the space group (S.G.) Immm (no. 71) with a=4.3679(9)angstrom, b=8.728(2) angstrom, c=16.378(4) angstrom, and V=624.4(2) angstrom(3). This compound is isotypic with YIrGe2 having a Ge10Pt4 subunit composed of edge-sharing five- and six-membered rings. SmPtGe2 shows a metallic conductivity from room temperature down to 2 K. The magnetic susceptibility measurement showed a 3+ oxidation state for the samarium. Sm2Pt3Ge5 crystallizes in the S.G. Ibam (no. 72) with a=10.174(1) angstrom, b=11.761(2) angstrom, c=6.2142(8) angstrom, and V=743.6(2) angstrom(3). It is isotypic with U2Co3Si5 with a structure closely related to ThCr2Si2