  In this paper we present calculations on the electronic band structure of a
two-dimensional lateral superlattice subject to a perpendicular magnetic field
by employing a projection operator technique based on the ray-group of
magnetotranslation operators. We construct a new basis of appropriately
symmetrized Bloch-like wavefunctions as linear combination of well-localized
magnetic-Wannier functions. The magnetic field was consistently included in the
Wannier functions defined in terms of free-electron eigenfunctions in the
presence of external magnetic field in the symmetric gauge. Using the above
basis, we calculate the magnetic energy spectrum of electrons in a lateral
superlattice with bi-directional weak electrostatic modulation. Both a square
lattice and a triangular one are considered as special cases. Our approach
based on group theory handles the cases of integer and rational magnetic fluxes
in a uniform way and the provided basis could be convenient for further both
analytic and numerical calculations.
