  We computed the actions for the 1D N=5 sigma-models with respect to the two
inequivalent (2,8,6) multiplets. 4 supersymmetry generators are manifest, while
the constraint originated by imposing the 5-th supersymmetry automatically
induces a full N=8 off-shell invariance. The resulting action coincides in the
two cases and corresponds to a conformally flat 2D target satisfying a special
geometry of rigid type. To obtain these results we developed a computational
method (for Maple 11) which does not require the notion of superfields and is
instead based on the nowadays available list of the inequivalent
representations of the 1D N-extended supersymmetry. Its application to
systematically analyze the sigma-models off-shell invariant actions for the
remaining N=5,6,7,8 (k,8,8-k) multiplets, as well as for the N>8
representations,only requires more cumbersome computations.
