New results on the low-T phase diagram of U1−xThxBe13: A thermodynamic study

Abstract We report on low-temperature thermal-expansion and specific-heat measurements on single crystals of the heavy-fermion superconductor UBe 13 . A new “line of anomalies”, B *( T ), in the superconducting state is discovered. The evolution of this feature is studied as a function of Th doping on several U 1− x Th x Be 13 polycrystals ( x ⩽0.03), giving rise to a new “line of anomalies”, T L ( x ), in the T – x phase diagram. T L ( x ) hits the multi-critical point at x cr ≈0.019 and merges smoothly into the T c2 line that marks the lower of the two phase transitions at x > x cr . Our data strongly suggest that the anomaly at T L ( x ) represents the precursor of the transition at T c2 ( x ) for 0.019 x 1− x Th x Be 13 are discussed.