  It is shown that the calculation of Dirac operator for the spherical
coordinate system with spherical Dirac matrices and using the spin connection
formalism is in the contradiction with the definition of standard Dirac
operator in the spherical Minkowski coordinate system. It is shown that such
contradiction one can avoid by introducing a canonical conjugated covariant
derivative for the spinor field. The Dirac equation solution on the Reissner -
Nordstr\"om background is obtained. The solution describes a bound state of a
charged particle.
