Taking Kaluza seriously leads to a non-gauge-invariant electromagnetic   theory in a curved space-time
  Kaluza's mertic with the cylinder condition is considered without the weak gravitational field approximation. It is shown that these hypoteses lead to a non-gauge-invariant electromagnetic theory in a curved space-time. The problem of electro-gravitational unification is considered from this point of view. 
Luca Fabbri