Original sentence: A general affine connection has enough degrees of freedom to describe both the gravitational and electromagnetic field.In the last 30 years, research on unified field theories shifted towards regarding the affine connection as the geometric representation of electromagnetism (works of Kaare Borchsenius, Robert McKellar, Marco Ferraris and Jerzy Kijowski, V.Ponomarev and Yuri Obukhov, Richard Hammond, and Nikodem Poplawski).See however, Ragusa (1997, 2002) for a modern attempt of completion of  Einstein's original unification program.The connection generalizes an ordinary derivative of a vector into a coordinate-covariant derivative and the electromagnetic potential generalizes it into a U(1)-covariant derivative, so both objects have the same purpose: to preserve the correct transformation properties under certain symmetries.The gravitational field is represented in the Lagrangian by the symmetric part of the Ricci tensor, as in the Einstein-Cartan theory, and the classical electromagnetic field tensor can be represented by the tensor of homothetic curvature (Weyl's segmental curvature tensor), or by the curl of the torsion vector (accordingly, the electromagnetic potential is represented by the nonmetricity vector or the torsion vector).The unified field theories with the electromagnetic field related to the affine connection are metric-affine, i.Unlike in the unified theories of Weyl, Kaluza, Einstein, and Schrodinger, where the electromagnetic field is associated with the metric tensor, relating the electromagnetic potential to the affine connection seems more natural.both the metric tensor and connection are dynamical variables  with respect to which the action is varied