Crystal electric field contribution to the thermoelectric power of the CeCoAl4 antiferromagnetic

We report on the thermoelectric power S(T), electrical resistivity and thermal conductivity measurements on the antiferromagnetic CeCoAl4 compound and on the nonmagnetic reference compound, LaCoAl4. The Neel temperature of CeCoAl4 is TN = 13.5K and a metamagnetic-like transition occurs in the magnetic field of about 7.5T. We show that the magnetic contribution to the thermoelectric power, Sf (T), exhibits a large peak due to the crystal electric field (CEF) at about 240K and a small anomaly around the ordering temperature. Surprisingly, the CEF related Sf (T) peak is close to the upper CEF excitation energy \(\Delta_2\) = 202K, in contrast to the usual case of the peak position being located at a fraction of the observed CEF energy level. The applicability of different theoretical and phenomenological models describing the temperature dependence of the Seebeck effect Sf (T) has been tested and finally a calculation is proposed, which incorporates a full CEF levels scheme.