The Dirac-Coulomb Problem: a mathematical revisit
  We obtain a symmetric tridiagonal matrix representation of the Dirac-Coulomb operator in a suitable complete square integrable basis. Orthogonal polynomials techniques along with Darboux method are used to obtain the bound states energy spectrum, the relativistic scattering amplitudes and phase shifts from the asymptotic behavior of the polynomial solutions associated with the resulting three-term recursion relation. 
A. D. Alhaidari, H. Bahlouli, M. E. H. Ismail
math-ph hep-th math.MP quant-ph