Phase transition in the superconducting state of ${\mathrm{U}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Th}}_{\mathrm{x}}$${\mathrm{Be}}_{13}$ (x=0–0.06)

We report results of specific-heat measurements and the observation of a new phase transition in the superconducting state of ${\mathrm{U}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Th}}_{\mathrm{x}}$ ${\mathrm{Be}}_{13}$ compounds for a narrow range of x values. Although the nature of this transition cannot be unambiguously established, its occurrence is important with regard to the characterization of the superconducting state in these compounds.