Comment on "Solutions of the Dirac equation with an improved expression of the Rosen-Morse potential energy model including Coulomb-like tensor interaction"

The Nikiforov-Uvarov polynomial method employed by Aguda (Can. J. Phys. 2013, 91: 689. doi:10.1139/cjp-2013-0109) to solve the Dirac equation with an improved Rosen-Morse potential plus a Coulomb-like tensor potential is shown to be inappropriate because the conditions of its application are not fulfilled. We clarify the problem and construct the correct solutions in the spin and pseudospin symmetric regimes via the standard method of solving differential equations. For the bound states, we obtain the spinor wave functions in terms of the generalized hypergeometric functions F-2(1)(a, b, c; z) and in each regime we show that the energy levels are determined by the solutions of a transcendental equation that can be solved numerically.