  We find a non-perturbative saddle-point solution for the non-linear sigma
model proposed by Finkelstein for interacting and disordered electronic
systems. Spin rotation symmetry, present in the original saddle point solution,
is spontaneously broken at one-loop, as in the Coleman-Weinberg mechanism. The
new solution is singular in both the disorder and triplet interaction
strengths, and it also explicitly demonstrates that a non-trivial ferromagnetic
state appears in a theory where the disorder average is carried out from the
outset.
