Evidence for the existence of two variants of UBe13

Abstract Low-temperature specific-heat and thermal-expansion measurements on high-quality single crystals of the heavy-fermion superconductor UBe 13 combined with literature results give evidence for the existence of two variants of this compound. They can be classified according to their superconducting transition temperatures into H-type (high T c : 0.85 ⩽ T c ⩽ 0.95K) and L-type (low T c : T c ≈ 0.75K) UBe 13 . A comparative investigation of both types reveals striking differences both above and below T c .