  We analyze the point-group symmetries of generic multiband tight-binding
models with respect to the transformation properties of the effective
interactions. While the vertex functions in the orbital language may transform
non-trivially under point-group operations, their point-group behavior in the
band language can be simplified by choosing a suitable Bloch basis.We first
give two analytically accessible examples. Then we show that, for a large class
of models, a natural Bloch basis exists, in which the vertex functions in the
band language transform trivially under all point-group operations. As a
consequence, the point-group symmetries can be used to reduce the computational
effort in perturbative many-particle approaches such as the functional
renormalization group.
