Superconducting Phase Diagram of Rh₁₇S₁₅

We report on measurements of the magnetization up to 7 T, of the specific heat and electrical resistivity in fields up to 14 T, and of the magnetic susceptibility in fields up to 20 T of a polycrystalline sample of Rh₁₇S₁₅. Our data allow us to complement the superconducting phase diagram. The existence of narrow 4 d-band states (and thus of strong electronic correlations that seem not to provide magnetic correlations) is supported by the moderately high electronic contribution to the specific heat of about 107 mJ/molK², favoring the existence of a strong superconducting interaction. This fact, and the remarkably high upper critical field (exceeding the simple Pauli limit by a factor of two), give evidence of the uncommon nature of the superconductivity in Rh₁₇S₁₅.