Spin-Triplet p-Wave Superconductivity Revealed under High Pressure in UBe13

To unravel the nature of the superconducting symmetry of the enigmatic 5f heavy-fermion UBe13, the pressure dependence of the upper critical field and of the normal state are studied up to 10 GPa. Remarkably, the pressure evolution of the anomalous Hc2(T,P) over the entire pressure range up to 5.9 GPa can be successfully explained by the gradual admixture of a field-pressure-induced Eu component in an A1u spin-Triplet ground state. This result provides strong evidence for parallel-spin pairing in UBe13, which is also supported by the recently observed fully gapped excitation spectrum at ambient pressure. Moreover, we have also found a novel non-Fermi-liquid behavior of the resistivity, ρ(T)∼Tn (nâ1), which disappears with the collapse of the negative magnetoresistance behavior and the existence of a superconducting ground state around P=6 GPa, suggesting a close interplay between Kondo scattering and superconductivity.