Thermoelectric properties of Yb 5 Si 3

We report the thermoelectric properties of valence fluctuating material Yb5Si3. The temperature dependent Seebeck coefficient of Yb5Si3 shows a negative peak at 10 K and positive broad peak around 100 K together with two sign changes. Such a behavior is different from that of typical heavy fermion systems. We demonstrate that the thermoelectric properties of Yb5Si3 including the electrical resistivity are most likely caused by the heterogeneous Yb valence states reflecting the crystallographically inequivalent Yb sites.