Unconventional properties of the noncentrosymmetric superconductor Re8NbTa

Re-based superconductors provide a rich platform for the study of unconventional superconductivity. We have investigated the superconducting properties of Re8NbTa, a new noncentrosymmetric cubic (α-Mn structure) rhenium-based ternary superconductor using transport, magnetization, specific-heat, and muon-spin rotation/relaxation (μSR) measurements. Specific-heat and transverse field μSR measurements suggest moderately coupled fully gapped superconductivity, well described by BCS theory. However, our zero-field μSR measurements reveal a small internal field onsetting around the superconducting Tc, indicating the unconventional superconducting ground state.