  We consider a band of fermions in two space dimensions with a flux phase
(relativistic) dispersion relation coupled to a local magnetic impurity via an
$ s-d$ interaction. This model describes spinons of a flux phase and it is also
a qualitative model of the quasiparticles in a $d_{x^2-y^2}$ superconductor. We
find a zero-temperature phase transition at a finite coupling constant between
a weak coupling unscreened impurity state and a strong coupling regime with a
Kondo effect. We use large-$N$ methods to study the phase transition in this
Kondo system away from marginality. The Kondo energy scales linearly with the
distance to the transition . The zero-field magnetic suceptibility at zero
temperature diverges linearly. Similar behavior is found in the $T$-matrix
which shows a resonance at the Kondo scale. However, in addition to this simple
scaling, we always find the presence of logarithmic corrections-to-scaling.
Such behavior is typical of systems at an upper critical dimension. We derive
an effective fermion model in one space dimension for this problem. Unlike the
usual Kondo problem, this system has an intrinsic multichannel nature which
follows from the spinor structure of $2+1$-dimensional relativistic fermions.
