  We prove a concentration result of a Bloch eigenstate in a periodic channel
under a constant gauge. In the semi-classical limit $h--> 0$ these eigenstates
concentrate near a maximizer of the scalar potential of the associated
Schrodinger operator, provided the constant gauge converges to a critical value
from above. This is in contrast with the ground states which concentrate for
any gauge in this limit near a minimizer of the scalar potential.
