  It has been proposed recently that interacting Symmetry Protected Topological
(SPT) phases can be classified using cobordism theory. We test this proposal in
the case of fermionic SPT phases with Z/2 symmetry, where Z/2 is either
time-reversal or an internal symmetry. We find that cobordism classification
correctly describes all known fermionic SPT phases in space dimension less than
or equal to 3 and also predicts that all such phases can be realized by free
fermions. In higher dimensions we predict the existence of inherently
interacting fermionic SPT phases.
