Thermodynamics and magnetism in Th(x)U(1-x)Be(13-y)B(y)

We report specific heat and muon Spin Rotation (mu-SR) measurements on Th (x = 0.019) and/or B (y = 0.03) substituted UBe(13). The specific heat data show that either Th or B substitution reduces the Kondo temperature T(sub K) and increases the entropy at the superconducting transition by almost 20 percent, indicating an enhanced density of states. However, whereas mu-SR shows clear evidence for magnetic correlations for Th substitutions (x is between 0.019 and 0.043), no magnetism is observed for B substitutions. The enhanced specific heat jump in the B-substituted material is associated with a change in the superconducting properties as T(sub K) is reduced.