$K\ne 0$ bands in ${}_{}{}^{158}{}_{}{}^{}\mathrm{Er}$ are obtained in Hartree-Fock calculations using a $-{\lambda }_K{J}^2$ term in the Hamiltonian. A single major shell for each proton and neutron and a surface $\delta$ interaction were used in the calculation. The large-$K$ bands have oblate shape and their Hartree-Fock field does not have time-reversal symmetry. Some of the $K\ne 0$ bands have quite low excitation energy. Their structure and the possible isomerism of the bandheads are discussed.

• Received 9 November 1979

DOI:https://doi.org/10.1103/PhysRevLett.45.1238