Superconductivity in W ₅ Si ₃ -type compound Nb ₅ Si ₂ Al

Abstract We discovered a new superconductor Nb 5 Si 2 Al ( T c = 2.6 K), crystalizing with a W 5 Si 3 -type structure. Field dependent magnetization demonstrated a type-II superconducting behavior. The μ 0 H c2 ( T ) was described with the GL model rather than the WHH theory, and it did not exceed the Pauli paramagnetic limiting field. Critical fields μ 0 H c1 (0) and μ 0 H c2 (0) were estimated to be 1.65 mT and 2.31 T, respectively. The sharp specific heat jump Δ C el / γT c was observed at T c , and the temperature dependence revealed a BCS-type isotropic gap within a weak-coupling regime. Comparing other superconductors with the W 5 Si 3 -type structure in terms of band filling revealed that T c obeyed an empirical relationship.