  The orbital basis is natural when one needs to calculate the effect of local
interactions or to unravel the role of orbital physics in the response to
external probes. In systems with nonsymmorphic point groups, such as the
iron-based superconductors, we show that symmetries that emerge in observable
response functions at certain wave vectors are absent from generalized
susceptibilities calculated with tight-binding Hamiltonians in the orbital
basis. Such symmetries are recovered only when the generalized susceptibilities
are embeded back to the continuum using appropriate matrix elements between
basis states. This is illustrated with the case of LiFeAs and is further
clarified using a minimal tight-binding Hamiltonian with non-symmorphic space
group.
