Improving the dimensionless figure of merit $Z\phantom{\rule{0}{0ex}}T$ is perhaps the most important topic in thermoelectric energy conversion. $Z\phantom{\rule{0}{0ex}}T$ depends oppositely on the electrical and thermal conductivities of a material, though, and they both depend on the mobility of electrons. This interdependence makes simultaneous optimization of both conductivities a real challenge. Spin caloritronics may offer a way forward: The authors propose a device to exploit the spin Nernst and inverse spin Hall effects, to break the interdependence of the conductivities and offer alternate strategies for waste-heat scavenging.