  We investigate the interplay of onsite Coulomb repulsion and various
mechanisms breaking the fourfold lattice symmetry in a three-band model for the
iron planes of iron-based superconductors. Using cluster-perturbation theory
allows us to locally break the symmetry between the x- and y-directions without
imposing long-range magnetic order. Previously investigated anisotropic
magnetic couplings are compared to an orbital-ordering field and anisotropic
hoppings. We find that all three mechanisms for a broken rotational symmetry
lead to similar signatures once onsite interactions are strong enough to bring
the system close to a spin-density wave. The band distortions near the Fermi
level are independent of differences between the total densities found in xz
and yz orbitals.
