Thermoelectricity of URu₂Si₂: Giant Nernst effect in the hidden-order state

We present a study of Nernst and Seebeck coefficients in the heavy-fermion compound URu₂Si₂, which hosts a phase transition of unsettled origin. A giant Nernst signal of unprecedented magnitude was found to emerge in the ordered state. Moreover, our analysis of the Seebeck and Hall data indicates that the ordering leads to a sudden increase in the entropy per itinerant electron and to a drastic decrease in the scattering rate.