We present the thermopower $S\left(T\right)$ and the resistivity $\rho \left(T\right)$ of ${\mathrm{Lu}}_{1-x}{\mathrm{Yb}}_x{\mathrm{Rh}}_2{\mathrm{Si}}_2$ in the temperature range $3<T<300\mathrm{K}$. $S\left(T\right)$ is found to change from two minima for dilute systems $(x<0.5)$ to a single large minimum in pure $\mathrm{Yb}{\mathrm{Rh}}_2{\mathrm{Si}}_2$. A similar behavior has also been found for the magnetic contribution to the resistivity ${\rho }_{\mathrm{mag}}\left(T\right)$. The appearance of the low-$T$ extrema in $S\left(T\right)$ and ${\rho }_{\mathrm{mag}}\left(T\right)$ is attributed to the lowering of the Kondo scale $k_B{T}_K$ with decreasing $x$. The evolution of the characteristic energy scales for both the Kondo effect and the crystal electric field splitting ${\Delta }_{\mathrm{CEF}}$ are deduced. An extrapolation of $T_K$ to $x=1$ allows us to estimate the Kondo temperature of $\mathrm{Yb}{\mathrm{Rh}}_2{\mathrm{Si}}_2$ to $29\mathrm{K}$. For pure $\mathrm{Yb}{\mathrm{Rh}}_2{\mathrm{Si}}_2$, $T_K$ and ${\Delta }_{\mathrm{CEF}}∕k_B$ lie within one order of magnitude and thus the corresponding extrema merge into one single feature.

• Received 17 October 2007

DOI:https://doi.org/10.1103/PhysRevB.77.104412