  We report a novel scale-independent, Aharonov-Bohm flux controlled crossover
from critical orthogonal to critical unitary statistics at the disorder induced
metal insulator transition. Our numerical investigations show that at the
critical point the level statistics are definitely distinct and determined by
fundamental symmetries. The latter is similar to the behavior of the metallic
phase known from random matrix theory. The Aharonov-Bohm flux dependent
crossover is characteristic of the critical ensemble.
