  We present a mechanism to generate complex phases from real 4+1 dimensional
couplings in a model of weak interactions through dimensional reduction of a
gauge theory. The orbifolding of a 4+1 dimensional Sp(4) \times U(1) group is
the minimal setup which provides both CP violation and an SU(2) \times U(1)
structure. We show that grand unification requires at least SO(11).
