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

We report specific heat and {mu}SR measurements on Th ({ital x} =0.019) and/or B ({ital y}=0.03) substituted UBe{sub 13}. The specific heat data show that either Th or B substitution reduces the Kondo temperature {ital T}{sub {ital 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{lt}{ital x}{lt}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 {ital T}{sub {ital K}} is reduced.