  A Kondo model for three spin-one-half impurities placed at the vertices of an
equilateral triangle is studied using the numerical renormalization-group
method. The impurity spins can form two frustrated doublets which, because of
the rotation symmetry, couple equally to the conduction band. Over a broad
range of antiferromagnetic RKKY interaction strengths, this degeneracy drives
the system to one of two novel, non-Fermi-liquid fixed points. Potential
scattering is a relevant perturbation at one of these fixed points, but is
marginal throughout the second regime.
