Superconducting ground state of a strongly interacting electron system: UBe13

Very recently it has been demonstrated that UBe13, in spite of its seemingly unfavourable normal-state properties, is a bulk superconductor with a critical temperature T /SUB c/ of about 0.9 K. The occurrence of superconductivity in UBe13 is particularly surprising since the non-magnetic compounds LaBe13, LuBe13 and ThBe13 are not superconducting above 0.45 K. Both the superconducting and normal state properties of UBe13, respectively, clearly indicate that they must be dominated by the presence of 5f electrons on the U ions. The low-temperature properties of UBe13 are indeed very similar to those of CeCu2Si2, a compound whose anomalous behaviour is thought to arise from strong interactions of conduction electrons with the 4f electrons of the Ce ions. Here we should like to discuss some of the experimentally determined properties of UBe13, mainly intending to initiate further theoretical work considering the possible ground states of strongly interacting electronic systems in solids