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Abstract:
Low-temperature measurements (200 mK≲T≲18 K) of the specific heat C(T) of polycrystalline UBe13 show that the normal-state electronic specific heat Cn(Tc)/Tc remains virtually constant at applied magnetic fields of B=1, 2, 4, and 8. Suggestions to explain the maintenance of the entropy balance between the normal and the superconducting state are discussed. With B=13 T, C(T) is decreased below 3 K compared to the zero-field data, and increased above this temperature. The entropy of the electron system increases linearly above 10 K without indication of saturation. The sharp discontinuity of C(T) at the transition to the superconducting state and the large dc Meissner effect measured in the same compound suggest that UBe13 is a very homogeneous superconductor [Bc2(0)apeq210 T]. From isothermal magnetization measurements at T=100 mK, we obtain Bc1apeq24.4 mT and, for the Ginzburg-Landau parameter, κapeq2100.
