Periodic orbit resonances in layered metals in tilted magnetic fields

The frequency dependence of the interlayer conductivity of a layered Fermi liquid in a magnetic field that is tilted away from the normal to the layer s is considered. For both quasi-one- and quasi-two-dimensional systems reso nances occur when the frequency is a harmonic of the frequency at which the magnetic field causes the electrons to oscillate on the Fermi surface with in the layers. The intensity of the different harmonic resonances varies si gnificantly with the direction of the field. The resonances occur for both coherent and weakly incoherent interlayer transport and so their observatio n does not imply the existence of a three-dimensional Fermi surface. [S0163 -1829(99)51240-X].