New Phase Diagram for (U,Th) Be13: A Muon-Spin-Resonance and Hc1 Study

Zero-field muon-spin-resonance and lower-critical-field data are presented for a wide range of Th concentrations in U1-x,Thx,Be13, spanning the region where both a superconducting and a second, lower-temperature phase transition are observed. OverallT-xphase boundaries are assigned and discussed according to the nature of the lower phase transition. Arguments for associating the lower phase with a possible magnetic (time-reversal-violating) superconducting state are given.