Nonlinear (4,8,4) multiplet of N=8, d=1 supersymmetry

We construct a nonlinear version of the d=1 off-shell N=8 multiplet (4,8,4), proceeding from a nonlinear realization of the superconformal group OSp(4⋆|4) in the N=8, d=1 analytic bi-harmonic superspace. The new multiplet is described by a double-charged analytic Goldstone superfield q1,1 subjected to some nonlinear OSp(4⋆|4) covariant harmonic constraints. We construct the most general N=8 supersymmetric actions of q1,1 and find the general expression for the bosonic target metric in terms of the original analytic Lagrangian superfield density which is thus the target geometry prepotential. It also completely specifies the scalar potential. The metric is conformally flat and, in the SO(4) invariant case, is a deformation of the metric of S4.