Peltier's and Thomson's coefficients of thermoelectric phenomena in the observable formulation

Four transport coefficients characterize the thermoelectric properties of materials. Three of them are widely measured and studied. But the number of references on the Peltier coefficient are very limited. This unequal result is a consequence of the Onsager reciprocal relation (ORR). A review on the preciseness and accuracy of Peltier coefficient measurements has been developed in this paper. Thus we can appreciate a low level in the experimental confirmation for the ORR. In order to describe the thermoelectric processes in an advantageous way, the observable formulation has been used. This is characterized by the electric potential measured at the probe terminals and for the heat flux which the conductor laterally dissipates. The energy balance provides the basic relationships among the observables and the Peltier and Thomson coefficients. A new way for measuring the Peltier coefficient has been suggested.