Superconducting properties of the spin Hall candidate Ta3Sb with eightfold degeneracy

We report the synthesis and characterization of phase pure Ta3Sb, a material predicted to be topological with eightfold degenerate fermionic states [Bradlyn et al., Science 353, aaf5037 (2016)] and to exhibit a large with Tc ??? 0.67 K in both electrical resistivity ??(T ) and specific heat c(T ) measurements. Field-dependent measurements yield the superconducting phase diagram with an upper critical field of Hc2(0) ??? 0.95 T, corresponding to a superconducting coherence length of ?? ??? 18.6 nm. The gap ratio deduced from specific heat anomaly 2.6.0/kBTc is 3.46, a value close to the Bardeen-Cooper-Schrieffer value of 3.53. From a detailed analysis of both the transport and thermodynamic data within the Ginsburg-Landau (GL) framework, a GL parameter of ?? ??? 90 is obtained, identifying Ta3Sb as an extreme type-II superconductor. The observation of superconductivity in an eightfold degenerate fermionic compound with topological surface states and predicted large spin Hall conductance positions Ta3Sb as an appealing platform to further explore exotic quantum states in multifold degenerate systems.