Non-Fermi-liquid behavior in the specific heat over two decades of temperature in doped UPt3

We have discovered, in contrast with most dopants M, that Hf (Zr) can be doped to quite high levels in U_1-xM_xPt₃, up to x=0.15 (0.30). Above 5% doping, the temperature dependence of the low-temperature upturn in C/T (specific heat divided by temperature) changes from T³lnT (indicative of spin fluctuations) to TlnT [indicative of non-Fermi-liquid (NFL) behavior]. The specific heat NFL temperature dependence has been measured down to 0.1 K and is seen over more than two decades in temperature. The field dependence of the NFL specific heat is small, consistent with a quadrupolar moment model interpretation. A possible reason for the NFL behavior is discussed.