  We have studied magnetotransport of a degenerate two-dimensional electron gas
in a Hall sample in the Knudsen regime, when the mean free paths of electrons
with respect to their collisions with each other and with impurities are much
larger than the width of the sample. In contrast to the usually considered
symmetric sample, whose both its edges reflect electrons diffusely, we
considered an asymmetric sample, one edge of which reflects them diffusely,
while the other specularly. It is shown that in such structure in low magnetic
fields the Hall coefficient is parametrically large in comparison with its
standard value. Also the situation is discussed when all types of scattering
can be neglected except for scattering at the edges of the sample.
