  In systems described by the scattering theory, there is an upper bound, lower
than Carnot, on the efficiency of steady-state heat to work conversion at a
given output power. We show that interacting systems can overcome such bound
and saturate, in the thermodynamic limit, the much more favorable
linear-response bound. This result is rooted in the possibility for interacting
systems to achieve the Carnot efficiency at the thermodynamic limit without
delta-energy filtering, so that large efficiencies can be obtained without
greatly reducing power.
