  The two-dimensional Kondo lattice model with both nearest and next-nearest
neighbor exchange interactions is studied within a mean-field approach and its
phase diagram is determined. In particular, we allow for lattice translation
symmetry breaking. We observe that the usual uniform inter-site order parameter
is never realized, being unstable towards other more complex types of order.
When the nearest neighbor exchange J_1 is ferromagnetic the flux phase is
always the most stable state, irrespective of the value of the
next-nearest-neighbor interaction J_2. For antiferromagnetic J_1, however,
either a columnar or a flux phase is realized, depending on conduction electron
filling and the value of J_2.
