  A possible scheme of realizing shell model calculations for heavy nuclei is
based on a deformed basis and the projection technique. Here we present a new
development for odd-odd nuclei, in which one starts with triaxially-deformed
multi-quasi-particle configurations, builds the shell-model space through exact
three-dimensional angular-momentum-projection, and diagonalizes a two-body
Hamiltonian in this space. The model enables us to study the old problem of
signature inversion from a different view. With an excellent reproduction of
the experimental data in the mass-130 region, the results tend to interpret the
phenomenon as a manifestation of dynamical drift of the rotational axis with
presence of axial asymmetry in these nuclei.
