Nanogranular Thermoelectrics

We investigate thermopower and thermoelectric coefficient of nano-granular materials at large tunneling conductance between the grains, g_{T} >> 1. We show that at intermediate temperatures, T >= g_{T}\delta, where \delta is the mean energy level spacing for a single grain, electron-electron interaction leads to an increase of the thermopower with decreasing grain size. We discuss our results in the light of new types of thermoelectric materials and present the behavior of the figure of merit depending on system parameters.