  Wave phenomena in bianisotropic media have been broadly scrutinized in
classical electrodynamics, as these media offer additional degrees of freedom
to engineer electromagnetic waves. However, all investigations concerning such
systems have so far been limited to stationary (time-invariant) media.
Temporally varying the magnetoelectric coupling manifesting bianisotropy
engenders a unique prospect to manipulate wave-matter interactions in new ways.
In this paper, we theoretically contemplate electromagnetic effects in weakly
dispersive bianisotropic media of all classes when the corresponding
magnetoelectric coupling parameter suddenly jumps in time, creating a time
interface in spatially uniform bianisotropic media. We investigate scattering
effects at such time interfaces, revealing novel polarization- and
direction-dependent phenomena. We anticipate that our work paves the road for
further exploration of time-varying bianisotropic metamaterials (metasurfaces)
and bianisotropic photonic time crystals, thus opening up interesting
possibilities to control wave polarization and amplitude in reciprocal and
nonreciprocal manners.
