  The Anderson impurity model for finite values of the Coulomb repulsion $U$ is
studied using a slave boson representation for the empty and doubly occupied
$f$-level. In order to avoid well known problems with a naive mean field theory
for the boson fields, we use the coherent state path integral representation to
first integrate out the double occupancy slave bosons. The resulting effective
action is linearized using {\bf two-time} auxiliary fields. After integration
over the fermionic degrees of freedom one obtains an effective action suitable
for a $1/N_f$-expansion. Concerning the constraint the same problem remains as
in the infinite $U$ case. For $T \rightarrow 0$ and $N_f \rightarrow \infty$
exact results for the ground state properties are recovered in the saddle point
approximation. Numerical solutions of the saddle point equations show that even
in the spindegenerate case $N_f = 2$ the results are quite good.
