CeCu2Si2 and UBe13: new questions - old answers?

Abstract Non-Fermi-liquid (NFL) temperature dependences of both the resistivity ρ( T ) and the Sommerfeld coefficient γ( T ) are observed for normal-state CeCu 2 Si 2 and UBe 13 . For the former compound, the NFL effects are related to the suppression (via pressure or suitable composition) of the spin-density-wave (SDW)-type `phase A' ( T A →0). Upon approaching the quantum critical point, ρ( T ) and γ( T ) behave very disparately, indicating a decoupling of the itinerant and local 4 f parts of the heavy-fermion quasiparticles. Similar observations are made with UBe 13 for which, however, no magnetic phase transition could so far be established. New anomalies are discovered in superconducting U 1− x Th x Be 13 with 0≤ x x cr =0.019.