  Motivated by a recent experiment, we study the microwave-induced
photoconductivity of a two-dimensional electron gas arising from
intra-Landau-level transitions within a model where the electrons are subject
to a unidirectional periodic potential in addition to a weaker impurity
potential. With appropriate identifications, our results can be compared to
experiment and allow us to explain the sign of the photocurrent, its dependence
on magnetic field and microwave frequency as well as the microwave-induced
suppression of the Shubnikov-deHaas oscillations.
