Superconductivity in the Platinum GermanidesMPt4Ge12(M=Rare−Earthor Alkaline-Earth Metal) with Filled Skutterudite Structure

Abstract

New germanium-platinum compounds with the filled-skutterudite crystal structure were synthesized. The crystal structure and composition were investigated by x-ray diffraction and microprobe analysis. Magnetic susceptibility, specific heat, and electrical resistivity measurements evidence superconductivity in ${\mathrm{LaPt}}_4{\mathrm{Ge}}_{12}$ and ${\mathrm{PrPt}}_4{\mathrm{Ge}}_{12}$ below 8.3 K. The parameters of the normal and superconducting states were established. Strong coupling and a crystal electric field singlet ground state is found for the Pr compound. Electronic structure calculations show a large density of states at the Fermi level. Similar behavior with lower $T_c$ was observed for ${\mathrm{SrPt}}_4{\mathrm{Ge}}_{12}$ and ${\mathrm{BaPt}}_4{\mathrm{Ge}}_{12}$.