Electronic heat capacity of the strongly exchange-enhanced metalUSn3

An analysis of the phonon heat capacity of ${\mathrm{USn}}_3$ is presented. This analysis is used to obtain the temperature dependence of the electronic heat-capacity coefficient, γ(T)=$C_e$/T. It is found that γ(T) decays smoothly from ${\gamma }_0$=171 mJ/mol ${\mathrm{K}}^2$ in the low-temperature limit to 24 mJ/mol $K^2$ at T=30 K and asymptotically approaches ∼20 mJ/mol ${\mathrm{K}}^2$. Band-structure calculations indicate a virtually temperature independent ${\gamma }_{\mathrm{BS}}$ of about 22 mJ/mol $K^2$. Thus the experimental γ(T) approaches ${\gamma }_{\mathrm{BS}}$ by about 30 K. The departure of the experimental curve below ∼30 K is most likely due to the onset of spin fluctuations. These fluctuations are local in nature since the area between the band and experimental γ curves up to 30 K is equal to 0.36R ln2. An analysis of new heat-capacity data below 10 K can be made consistent with the existence of a $T^3$lnT term, but subtraction of a realistic phonon heat-capacity contribution removes this term. The implication that this observation has on other spin fluctuators and heavy-fermion compounds is discussed.