Contributions to the diffusion thermopower of amorphous CuxSn100-x and Mg70Zn30 films

In situ thermopower S(T) measurements of quench-condensed amorphous Cu x Sn 100−x (25 ≤ x ≤ 70) and Mg 70 Zn 30 films are reported. S(T) shows a knee at about 30 K. We explained this structure as being caused by electronphonon interaction and so-called roton-like collective density excitations. In our analysis the sign as well as the absolute value of S(T) at low temperatures agree for the Sn rich samples with the free electron model.