de Haas-van Alphen Effect in Gadolinium

We have measured the de Haas-van Alphen effect in a single crystal of Gd, refined by solid-state electrolysis, observing four frequencies (in the range ${10}^5$-3×${10}^7$ G) near the $c$ axis and three frequencies in the basal plane. The faster oscillations identify with orbits on the third-zone sub-band Fermi surfaces of the relativistic augmented plane-wave calculations, if the sub-band energies are displaced by ± 0.57 eV by the ferromagnetic internal field.