Abstract: We are going to prove that the Monopole and the Coulomb fields are duals within the unifying structure provided by the Reissner-Nordström spacetime. This is accomplished when noticing that in order to produce the tetrad that locally and covariantly diagonalizes the stress-energy tensor, both the Monopole and the Coulomb fields are necessary in the construction. Without any of them it would be impossible to express the tetrad vectors that locally and covariantly diagonalize the stress-energy tensor. Then, both electromagnetic fields are an integral part of the same structure, the Reissner-Nordström geometry.

Key words: Einstein-Maxwell spacetime, classical general relativity, gauge field theories, symmetry and conservation laws