materials with a spontaneous nonreciprocal response, such as Tellegen (axion) media or
topological insulators. Surprisingly, it is proven that stratified Tellegen photonic crystals that
break simultaneously the space inversion and time-reversal symmetries have always
symmetric dispersion diagrams. Interestingly, we show that by combining chiral and
nonreciprocal materials the photonic band diagrams can exhibit a spectral asymmetry such …