Thermal expansion of polycrystalline UPt 2, UPt 3 and UPt 5

The thermal expansion of the polycrystalline compounds UPt ₂, UPt ₃ and UPt ₅ was measured in the temperature range 1.4 up to 80 K. Of particular interest is the spin-fluctuation compound UPt ₃, which, after recently being discovered to behave as a heavy-fermion superconductor, nowadays receives much attention. Its thermal expansion reveals a large anomalous contribution below 50 K. This contribution appears as a low-temperature upturn in a plot of α/ T versus T², and is associated with spin fluctuations. In the compounds UPt ₂ and UPt ₅ a similar upturn appears, although less pronounced. The thermal expansion data are compared with previously published specific heat data on the same samples.