Formation and destruction of the heavy-electron ground state in U compounds with AuBe_{5} crystal structure

The strong influence of changes of the chemical composition on the formation of a heavy-electron ground state is demonstrated in uranium intermetallic compounds crystallizing in the cubic ${\mathrm{AuBe}}_5$ structure. The most spectacular effect is the large enhancement of the low-temperature electronic specific heat in ${\mathrm{UPt}}_5$ when one Pt atom per formula unit is replaced by Au. ${\mathrm{UAuPt}}_4$ may be a heavy-electron superconductor.