The conjecture that unified nonlinear equations for gravitation and electromagnetism may lead directly to the Lorentz equation of motion for charged particles is discussed assuming a theory of connections on a principal bundle with SL(2,Q) as the structure group. It is shown that the Lorentz equation is a consequence of the field equations when the connection reduces to only one particular component, which may be identified with the electromagnetic potential. The proposed equations generalize, in a nontrivial way, the equations of gravitation and electrodynamics.