Local Geometry of the Fermi Surface

The electronic properties of normal metals have been under active study for several decades. In the 1950s and 1960s most investigations sought to describe the Fermi surfaces of metals. These studies were based on experimental data obtained as a re sult of numerous observations of particular phenomena responsive to the structure of the electronic spectra of metals and thus to band-structure calculations [lJ. The high-frequency properties of metals were also actively studied. These investiga tions were initiated by the development of the theory of the anomalous skin effect [2J. Later, significant achievements were reached in studies of the high-frequency properties of metals in the presence of an applied magnetic field. Cyclotron res onance in a parallel magnetic field [3], electromagnetic waves in metals [4]-[6J, size effects [7J, [8], Doppler shifted cyclotron resonance, and dopplerons [9], [10] were predicted in theoretical studies and repeatedly observed in experiments. This offered new scope for analysis of the properties of the electron system of metals. The main results of theoretical and experimental studies of the electronic charac teristics of metals performed during this period are expounded in several books and review articles (see, e. g. , [11]-[14], [16]). Great progress was also achieved in studies of the interaction between an elec tron system and the ultrasonic waves propagating in metals. At low temperatures (T < 10 K) the electrons produce a strong effect on the dispersion and attenuation of ultrasound waves.