We propose a five-band tight-binding model for the Fe-As layers of iron pnictides with the hopping amplitudes calculated within the Slater-Koster framework. The band structure found in DFT, including the orbital content of the bands, is well reproduced using only four fitting parameters to determine all the hopping amplitudes. The model allows to study the changes in the electronic structure caused by a modification of the angle $α$ formed by the Fe-As bonds and the Fe-plane and recovers the phenomenology previously discussed in the literature. We also find that changes in $α$ modify the shape and orbital content of the Fermi surface sheets.

12 pages, 6 eps figures. Figs 1 and 2 modified, minor changes in the text. A few references added