New non-unitary representations in a Dirac hydrogen atom
  New non-unitary representations of the SU(2) algebra are introduced for the case of the Dirac equation with a Coulomb potential; an extra phase, needed to close the algebra, is also introduced. The new representations does not require integer or half integer labels. The set of operators defined are used to span the complete space of bound state eigenstates of the problem thus solving it in an essentially algebraic way. 
R.P. Mart\'inez-y-Romero, J. Salda\~na-Vega and A.L. Salas-Brito