Multi-component order parameter for YBa2CuO7-δ and other high-Tc compounds

We suggest that the generalized Ginzburg-Landua free energy functional describing the superconducting phases of the 123 compounds requires at least two order parameters each one disappearing at a distinct critical temperature. We point out similarities to the heavy fermion system U1-xThxBe13, which has, however, cubic symmetry and therefore does not show the high anisotropy effects of the high Tc materials.