Measurement of the anisotropic Fermi velocity in Al

From an analysis of surface-Landau-lavel resonance at 36 GHz, we determine the Fermi velocity over characteristic portions of the Fermi surface of Al. By comparing the experimental velocities with calculated band velocities, we obtain corresponding values for the mass-enhancement parameter $\lambda$. Except near the intersections of the Fermi surface with the Brillouin-zone boundaries, the results are in good agreement with recent theoretical calculations of the anisotropic mass enhancement induced by the electron-phonon interaction.