Nernst effect of the intermediate valence compound YbAl₃: revisiting the thermoelectric properties

The Nernst effect and thermopower of the prototypical Yb-based intermediate valence compound YbAl3 were investigated. Different to the thermopower whose absolute values are enhanced with increasing temperature and assume a broad maximum at 175 K, the Nernst coefficient of YbAl3 is enhanced only below T approximate to 75 K. While the two quantities in the heavy-fermion compound CeCu2Si2 were recently found to be related by the anomalous Hall mobility due to the local asymmetric Kondo scattering, this theorem fails when being applied to YbAl3. Rather, the thermopower of YbAl3 is well described by a simple narrow-band model. We discuss the reason for this in terms of the intermediate valence nature of YbAl3 that is conceptually different from the local Kondo physics