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

We report specific heat and {mu}SR measurements on Th (x = 0.019) and/or B (y = 0.03) substituted UBe{sub 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%, indicating an enhanced density of states. However, whereas {mu}SR shows clear evidence for magnetic correlations for Th substitutions (0.019 < x < 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.