  We study thermoelectric currents of neutral, fermionic atoms flowing through
a mesoscopic channel connecting a hot and a cold reservoir across the
superfluid transition. The thermoelectric response results from a competition
between density-driven diffusion from the cold to the hot reservoir and the
channel favoring transport of energetic particles from hot to cold. We control
the relative strength of both contributions to the thermoelectric response
using an external optical potential in a nearly non-interacting and a
strongly-interacting system. Without interactions, the magnitude of the
particle current can be tuned over a broad range but is restricted to flow from
hot to cold in our parameter regime. Strikingly, strong interparticle
interactions additionally reverse the direction of the current. We
quantitatively model ab initio the non-interacting observations and
qualitatively explain the interaction-assisted reversal by the reduction of
entropy transport due to pairing correlations. Our work paves the way to
studying the coupling of spin and heat in strongly correlated matter using
spin-dependent optical techniques with cold atoms.
