Breakdown of hybridisation at elevated temperatures in some intermetallic compounds

The ‘classical’ s-d scattering theory is applied to account for the anomalous temperature dependence of the resistivity in some intermetallic compounds, which possess very narrow peaks in the electronic density of states, due to d or f states. At temperatures where ħ/τ_e-ph ≈ J, where τ_e-ph is the electron-phonon scattering time and J a hybridisation integral, the hybridisation is broken, and at higher temperatures the resistivity follows a linear ρ=a + bTlaw. The temperature-independent part a is due to phonons scattering the d or f states, into which the s electrons (which carry most of the electric current) are scattered by the hybridisation integral J. The b T term is due to phonon scattering of the more itinerant s (or p) states into s states. This term does not saturate because the mean free path of the s electrons is still about 10 interatomic spacings, even at high temperatures. The thermoelectric power has a maximum when ħ/τ_e-ph ≈ J.