  The field dependence of power factor for a layered thermoelectric material
with a closed Fermi surface in a quantizing magnetic field and at helium
temperatures has been studied in the geometry where the temperature gradient
and the magnetic field are perpendicular to the material lasyers. The
calculations are carried out in the constant relaxation time approximation. In
weak magnetic fields,the layered structure effects are shown to manifest
themselves in a phase retardation of power factor oscillations,increase of
their relativeb contribution, and certain reduction of the power factor in
whole.In highmagnetic fields,there exists an optimal range,where the power
factor reaches its maximum,with the corresponding value calculated for the
chosen parameters of the problem in the effective mass approximation being by
12%higher than that for real layered crystals.Despite low temperatures,the
power factor maximum obtained with those parameters in a magnetic field of 1T
has a value characteristic of cuprate thermoelectric materials at 1000K. For
this phenomenon to take place, it is necessary that the ratio between the free
path of charge carriers and interlayer distance should be equal to or larger
than 30000. However,in ultraquantum magnetic fields, the power factor
drastically decreases following the dependence P propto T^-3B^-6.The main
reason for this reduction is a squeeze of the Fermi surface along the magnetic
field in the ultraquantum limit owing the condensation of charge carriers on
the bottom of a single filled Landau subband.
