We investigate the photonic band diagrams of periodic structures formed by nonreciprocal materials (Tellegen or ferrite materials) and chiral media. It is shown that even though the space inversion and time reversal symmetries are broken in Tellegen photonic crystals, these structures are characterized by spectrally symmetric band diagrams.
Interestingly, it is demonstrated that by combining chiral and nonreciprocal materials the photonic band diagrams can become
asymmetric. Furthermore, our results suggest that the role of a
ferrite slab can be mimicked by two juxtaposed Tellegen media slabs with a spontaneous nonreciprocal response.