Character States and Generator Matrix Elements for $Sp(4) \supset SU(2)   \times U(1)$: Generic Representation
  A new set of polynomial states (to be called character states) are derived for $Sp(4)$ reduced to its $SU(2) \times U(1)$ subgroup, and the relevant generator matrix elements are evaluated for generic representations $(a,b)$ of $Sp(4)$. (The degenerate representations $(a,0)$ and $(0,b)$ were treated in our previous work and are also given in this paper). The group--subgroup in question is that of the seniority model of nuclear physics. 
N. Hambli, J. Michelson and R. T. Sharp