Abstract
Short-period square lateral superlattices are fabricated on a two-dimensional electron gas located close to the sample surface. For weak potential modulation, band conductivity dominates the low-field magnetoresistance leading to pronounced commensurability oscillations. For increasing potential modulation, band conductivity breaks down and scattering conductivity dominates indicating our beginning to resolve the internal structure of a Landau band. For strong potential modulation the maxima of the Shubnikov-de Haas oscillations split up into submaxima related to the number of flux quanta penetrating a unit cell.