High thermoelectric performance in metallic NiAu alloys via interband scattering.

Thermoelectric materials seamlessly convert thermal into electrical energy, making them promising for power generation and cooling applications. Although historically the thermoelectric effect was first discovered in metals, state-of-the-art research focuses on semiconductors. Here, we discover unprecedented thermoelectric performance in metals and realize ultrahigh power factors up to 34 mW m K in binary NiAu alloys, more than twice larger than in any bulk material above room temperature, reaching ∼ 0.5. In metallic NiAu alloys, large Seebeck coefficients originate from electron-hole selective scattering of Au electrons into more localized Ni states. This intrinsic energy filtering effect owing to the unique band structure yields a strongly energy-dependent carrier mobility. While the metastable nature of the Ni-Au system as well as the high cost of Au pose some constraints for practical applications, our work challenges the common belief that good metals are bad thermoelectrics and presents an auspicious route toward high thermoelectric performance exploiting interband scattering.