Experiments on the Heavy Electron Superconductors UBe13 and URu2Si2

A variety of ground states have been found in heavy electron compounds; nonmagnetic-normal conducting, nonmagnetic-superconducting, magnetic-normal conducting, and coexisting antiferromagnetic-superconducting. Superconducting heavy electron compounds, in particular, have attracted a great deal of attention because the superconductivity was unexpected and the superconducting properties are very unusual. This has led to the speculation that these materials may exhibit an unconventional type of superconductivity involving a new type of pairing and/or pairing mechanism. In this paper, we briefly review some recent experiments we have carried out on the heavy electron superconductors UBe13 and URu2Si2 in an effort to obtain information concerning the origin and nature of superconductivity in these remarkable materials.