Effect of Pressure on the Fermi Surface of Be

Measurements of the effect of hydrostatic pressure on five cross-sectional areas of the Fermi surface of Be are presented. The cross sections were determined from de Haas-van Alphen frequencies obtained with the field-modulation technique. Pressure derivatives were obtained in both solid He to {~}4 kbar and in fluid He, and results from the two pressure techniques were in excellent agreement in all cases. The most striking result is that for H{∥}[0001] the waist of the third-zone electron surface decreases while the hips of this surface increase. This behavior cannot be explained even in qualitative terms by free-electron considerations and is at variance with results inferred from recent magnetostriction data. Our results, however, are in substantial agreement with recent calculations by Tripp, Everett, Gordon, and Stark.