Direct evidence for electron-phonon interaction-driven phonon transport attenuation above ambient temperature

While the electron-phonon interactions (EPIs) have been predicted to strongly suppress phonon transport and lattice thermal conductivity (κL) above room temperature, direct experimental validation remains challenging because the observed reduction of κL in the doped materials is commonly a result of concurrent enhancement of EPIs and point-defect-induced phonon scattering (PDPS). Here, we circumvent this ambiguity through strategically designed aliovalent-alloying semiconductors (e.g., TiFe0.5+xNi0.5-xSb, −0.25 ≤ x ≤ 0.25), where the compositional deviations from x = 0 amplify EPIs while weakening PDPS. Experimentally, we observed a pronounced EPI-driven κL reduction of ∼50% at room temperature and ∼40% even at 1000 K as carrier concentration approaches 1 × 1022 cm−3. The carrier-induced phonon softening and the enhanced electron-phonon scattering rates collectively lead to this remarkable phonon transport attenuation. Our findings establish a quantitative framework for disentangling EPI effects on phonon transport in heavily doped semiconductors or metals, and provide insights into phonon engineering strategies for advanced thermal management materials design.