  We have studied the phase diagram and excitations of the spin-orbital model
derived for a three dimensional perovskite lattice, as in KCuF_3. The results
demonstrate that the orbital degeneracy drastically increases quantum
fluctuations and suppresses the classical long-range order near the
multicritical point in the mean-field phase diagram. This generates a
qualitatively new spin liquid, providing the first example of a valence bond
ground state in three dimensions.
