The mixed-valence compound ${\mathrm{YbInCu}}_4$ was investigated by electrical resistivity and ac specific heat at low temperatures and high pressures. At atmospheric pressure, its Kadowaki-Woods (KW) ratio $A/{\gamma }^2$ is 16 times smaller than the universal value $R_{\mathrm{KW}}(=1.0\times {10}^{-5}\mu \Omega ·\mathrm{cm}·{\mathrm{mol}}^2·{\mathrm{K}}^2·{\mathrm{mJ}}^{-2})$, but sharply increases to $16.5R_{\mathrm{KW}}$ at 27 kbar. The pressure-induced change in the KW ratio and deviation from $R_{\mathrm{KW}}$ are analyzed in terms of the change in $f$-orbital degeneracy $N$ and carrier density $n$. This analysis is further supported by a dramatic change in residual resistivity ${\rho }_0$ near 25 kbar, where ${\rho }_0$ jumps by a factor of 7.

• Received 7 September 2004

DOI:https://doi.org/10.1103/PhysRevLett.96.046405