  The internal symmetry group U(3,1) of the neutral vector fields with two
spins 0 and 1 is investigated. Massless fields correspond to the generalized
Maxwell equations with the gradient term. The symmetry transformations in the
coordinate space are integro-differential transformations. Using the method of
the Hamiltonian formalism the conservation tensors are found, and the quantized
theory is studied. The necessity to introduce an indefinite metric is shown.
The internal symmetry group U(3,1) being considered, after the transition to
electrodynamics, reduces to the U(2) group. It is shown that the group of dual
transformations is the subgroup of the group under consideration.
  All the linearly independent solutions of the equation for a free particle
obtained in terms of the projection matrix-dyads.
