Revision of the Phase Diagram of Superconducting U1-xThxBe13

Low-temperature specific-heat and thermal-expansion measurements on a single crystal of the heavy-fermion superconductor UBe{sub 13} reveal an anomaly in the superconducting state. The evolution of this feature is studied as a function of Th doping on several U{sub 1{minus}x}Th {sub x}Be{sub 13} polycrystals (x{le}0.03 ), giving rise to a new {open_quotes}line of anomalies,{close_quotes} T{sub L}(x), in the T-x diagram. The anomaly at T{sub L}(x) marks the precursor of the lower of the two phase transitions at x{gt}x{sub cr}{approx}0.019 . Implications for the interpretation of the phase diagram of superconducting U{sub 1{minus}x}Th {sub x}Be{sub 13} are addressed. {copyright} {ital 1998} {ital The American Physical Society}