Giant Nernst effect in a Kondo lattice close to a quantum critical point

We present a study of Nernst and Seebeck coefficients of the heavy-fermion superconductor CeCoIn${}_5$. Below 18 K, concomitant with a field-dependent Seebeck coefficient, a large sub-linear Nernst signal emerges with a magnitude drastically exceeding what is expected for a multi-band Fermi-liquid metal. In the mixed state, in contrast with all other superconductors studied before, this signal overwhelms the one associated with the motion of superconducting vortices. The results point to a hitherto unknown source of transverse thermoelectricity in strongly interacting electrons.