Thermopower Evolution in Yb( $$\hbox {Rh}_{1-x}\hbox {Co}_x$$ Rh 1 - x Co x ) $$_2\hbox {Si}_2$$ 2 Si 2 Upon 4f Localization

We present thermopower measurements on Yb( $\hbox {Rh}_{1-x}\hbox {Co}_x ) _2\hbox {Si}_2 . Upon cobalt substitution, the Kondo temperature is decreasing and the single large thermopower minimum observed for \hbox {YbRh}_2\hbox {Si}_2 splits into two minima. Simultaneously, the absolute thermopower values are strongly reduced due to a weaker exchange coupling between the 4f and the conduction electron states with increasing x. Pure...