Thermoelectric (TE) materials directly transform thermal into electrical energy and vice versa, making them promising for a plethora of applications in refrigeration or power generation. However, state-of-the-art semiconductors in the focus of current research so far have not made the leap into broad applications due to low power density and poor mechanical properties. Metallic systems would be superior in this regard, but remained largely neglected over the past decades due to their small Seebeck coefficient S. Here we realize high TE performance in metals via tuning of electronic interband scattering – an innovative enhancement principle cardinally different from those applied so far in semiconductors. In particular, we boost S by selectively reducing the mobility of holes as they scatter off localized Ni 3d states, leveraged by tuning of the electronic bandwidth. Using this paradigm, we recently discovered record-high power factors (PF) of 34 mWm−1K−2 in binary NixAu1-x alloys [1]. Despite this unprecedented TE performance (highest zT ≈ 0.5 among all metals [1]), metastability and high cost of NixAu1-x pose difficulties for applications. We have therefore continued our quest for metallic TE with superior functional properties from more abundant elements. Via a multi-step DFT-based screening method developed herein, we discover a new family of L12-ordered binary compounds, with ultrahigh PF up to 11 mWm−1K−2 near room temperature in Ni3Ge [2]. Moreover, we also realize high PF in the kagome metal Ni3In1-xSnx by scattering off topological flat bands born from geometrically frustrated Ni 3d orbitals [3]. References [1] Garmroudi, F.; Parzer, M.; Riss, A.; Bourgès, C.; Khmelevskyi, S.; Mori, T.; Bauer, E.; Pustogow, A., Sci. Adv. 9, eadj1611 (2023). [2] Garmroudi, F.; Di Cataldo, S.; Parzer, M.; Coulter, J.; Iwasaki, Y.; Grasser, M.; Stockinger, S.; Pázmán, S.; Witzmann, S.; Riss, A.; Michor, H.; Podloucky, R.; Khmelevskyi, S.; Georges, A.; Held, K.; Mori, T.; Bauer, E.; Pustogow, A., arXiv:2501.04891 [3] Garmroudi, F.; Serhiienko, I.; Parzer, M.; Riss, A.; Grasser, M.; Stockinger, S.; Khmelevskyi, S.; Pryga, K.; Wiendlocha, B.; Held, K.; Mori, T.; Bauer, E.; Pustogow, A., arXiv:2404.08067