Superconducting and Normal State Properties in the Ternary Silicide NbIrSi, TaIrSi and NbPtSi

The polycrystalline NbIrSi, TaIrSi and NbPtSi with an orthorhombic structure (space group Pnma) were synthesized by an arc-melting method. Electrical resistivity ρ(T) measurement in three compounds were performed from 0.28 to 300 K. ρ(T) of NbIrSi indicates typical metallic behavior with no superconducting transition down to 0.28 K. Superconducting-like behavior is observed around 0.5 K in TaIrSi, but zero resistivity cannot be observed down to 0.28 K. ρ(T) of NbPtSi shows superconductivity at 1.24 K. From ρ(T) in several magnetic fields, the upper critical field μ0Hc2(0) of NbPtSi is obtained to be 1.15 T.