We show analytically and numerically that the application of an external magnetic field to highly excited Rydberg excitons breaks all antiunitary symmetries in the system. Only by considering the complete valence band structure of a direct band gap cubic semiconductor, the Hamiltonian of excitons leads to the statistics of a Gaussian unitary ensemble (GUE) without the need for interactions with other quasi-particles like phonons. Hence, we give theoretical evidence for a spatially homogeneous system breaking all antiunitary symmetries.

Accepted for publication in Physical Review Letters