θ-TaN: Redefining the thermal conductivity limit of metallic materials

• θ-TaN achieves a room-temperature thermal conductivity of ~1100 W·m−1·K−1, nearly three times that of copper, shattering the long-held limit of ~400 W·m−1·K−1 for metals. • The exceptional thermal conductivity arises from the hexagonal crystal structure (space group P6m2) with rigid, interpenetrating covalent Ta-N networks that suppress phonon-phonon scattering while preserving metallic electron transport. • This experimental realization validates decades of theoretical predictions and introduces a new class of high-thermal-conductivity metals, offering transformative potential for thermal management in electronics, aerospace, and energy systems. • The study demonstrates that decoupling electron and phonon transport is possible in metallic systems, opening new avenues for designing ultrahigh-thermal-conductivity materials beyond traditional semiconductors and insulators.