Evidence for Varyingd-Band Occupancy across the Trivalent Rare-Earth Series

The resistivity of liquid Lu, which has been measured for the first time up to 1800°C, has a negative temperature coefficient. In the framework of structural-disorder scattering this means that $2k_{\mathrm{F}}$, the diameter of the Fermi sphere of conduction electrons, lies close to the wave number $K_p$ of the first peak of the structure factor. This is consistent with recent band-structure calculations by Duthie and Pettifor providing good evidence that the number of $s$ electrons per atom changes from about 0.5 for La to 1.5 for Lu.