UBe13: An Unconventional Actinide Superconductor

Abstract

Electrical-resistivity, magnetic-susceptibility, and specific-heat data reveal that U${\mathrm{Be}}_{13}$ is superconducting below 0.85 K. Highly anomalous low-temperature electronic properties in both the normal and superconducting states result in an enormous electronic specific-heat coefficient $\gamma =1.1\mathrm{}$ J/mole ${\mathrm{K}}^2$ and a corresponding magnetic susceptibility $\chi =1.5\mathrm{}\times {10}^{-2\mathrm{}}$ emu/mole. The superconducting state appears to be extremely stable with an initial slope of the temperature derivative of the critical field ${\left(\frac{\partial H_{c2\mathrm{}}}{\partial T}\right)}_{T_c}=-257\mathrm{}$ kOe/K.