Specific Heat and Thermal Conductivity of Superconducting UBe13 and UPt3 at Very Low Temperatures

Abstract

Non-exponential temperature dependences of various physical properties in the superconducting state of UBe₁₃ and UPt₃ have been put forward as evidence for unconventional superconductivity in these materials. We report new experimental results for the specific heat c_p and the thermal conductivity λ of UBe₁₃ and UPt₃ down to temperatures well below 0.1 K. In none of these measurements can an exponential temperature dependence be recognized. In some aspects, our data differ from those that were previously published. This indicates that sample purity and imperfection may be of importance.