High Thermoelectric Power Factor and Efficiency from a Highly Dispersive Band in Ba 2 Bi Au

In harvesting waste heat for electricity via thermoelectric materials, the figure of merit $z\phantom{\rule{0}{0ex}}T$ has stagnated at values below 3, as it is difficult to simultaneously achieve low lattice thermal conductivity yet high electronic conductivity. Using state-of-the-art first-principles techniques, the authors predict a tremendous $n$-type $z\phantom{\rule{0}{0ex}}T$ of 5 at 800 K in the full-Heusler compound Ba${}_{2}$BiAu, due to a ``pocket'' in a highly dispersive conduction band. A parallel study of Fe${}_{2}$TiSi allows the generalization that highly dispersive bands at off-symmetry points ought to be pursued for next-generation thermoelectrics.