We report on measurements of the low-temperature specific heat Cp(T, B) of the unconventional superconductor UBe13 in magnetic fields up to 7 T. At B≈2 T, a substantial change in the magnetic-field dependence of the temperature derivative of the magnetic-field induced contribution to the electronic specific heat CH(T, B), resulting from the flow of supercurrents around the vortices, is observed, suggesting a crossover between two different regions in the superconducting phase diagram of UBe13. For fields B >2 T, CH(T, B) exhibits a scaling behavior with respect to TB-1/2, which provides substantial evidence for the existence of point nodes in the quasiparticle excitation spectrum of the superconductor.

We report on results of low-temperature specific-heat measurements of the unconventional superconductors UBe13 and U0.9669Th0.0331 Be13 in external magnetic fields up to 7 T. For T ≪ Tc, or, respectively, Tc2 for the thoriated sample, the magnetic field-induced contribution to Cp(T,B) varies linearly with temperature, which is consistent with the temperature dependence of the specific heat due to the flow of supercurrent around the vortices. © 2000 Elsevier Science B.V. All rights reserved.