  We consider a spin-1/2 charged particle in the plane under the influence of
two idealized Aharonov-Bohm fluxes. We show that the Pauli operator as a
differential operator is defined by appropriate boundary conditions at the two
vortices. Further we explicitly construct a basis in the deficiency subspaces
of the symmetric operator obtained by restricting the domain to functions with
supports separated from the vortices. This construction makes it possible to
apply the Krein's formula to the Pauli operator.
