  We study the ground state properties of a quantum antiferromagnet in the
kagome lattice in the presence of a magnetic field, paying particular attention
to the stability of the plateau at magnetization 1/3 of saturation. While the
plateau is reinforced by certain deformations of the lattice, like the
introduction of structural defect lines and against an Ising anisotropy, ground
state correlations are seen to be quite different and the undistorted SU(2)
case appears to be rather special.
