Superconductivity in R${\mathrm{Pt}}_2$${\mathrm{B}}_2$C

Superconductivity for lanthanide platinum boron carbide quaternary intermetallic phases is reported. For R${\mathrm{Pt}}_2$${\mathrm{B}}_2$C, superconducting ${\mathit{T}}_{\mathit{c}}$’s are approximately 10 K for R=La and Y and 6 K for R=Pr, reflecting the influence of magnetic pair breaking. The crystal structure for one of the analogs, ${\mathrm{LaPt}}_2$${\mathrm{B}}_2$C, was determined by single-crystal x-ray diffraction. These materials are isostructural with the recently discovered R${\mathrm{Ni}}_2$${\mathrm{B}}_2$C superconductors, but apparently can accommodate some nonstoichiometry. The density of states at the Fermi level for ${\mathrm{LaPt}}_2$${\mathrm{B}}_2$C is estimated to be approximately 5 mJ/mole ${\mathrm{K}}^2$ through measurements of the critical fields and the normal-state susceptibility.