Monopole supersymmetries and the Biedenharn operator

10 pages. Plain TeX, no figures. Submitted to the Phys. Lett. BThe hidden supersymmetry of the monopole found by De Jonghe et al. is generalized to a spin $\\2$ particle in the combined field of a Dirac monopole plus a $\\lambda^2/r^2$ potential [considered before by D\'Hoker and Vinet], and related to the operator introduced by Biedenharn a long time ago in solving the Dirac-Coulomb problem. Explicit solutions are obtained by diagonalizing the Biedenharn operato