I propose a model for the upper-part of pf-shell, which consists of p1/2, p3/2, f5/2 and g9/2 single-particle orbits. While the pf-subshell (or d˜s-subshell, i.e. η˜=2,s˜1/2,d˜3/2,d˜5/2) is governed by the SU˜S˜T(4)⊗U˜L˜(6) symmetry, the g9/2 intruder state is governed by the seniority model. The nuclear states of 76Ge and 76Se are expressed as direct products of the d˜s subshell component and the g-subshell one. The five-dimensional quasispin formalism with seniority zero restriction is used for a classification in the g-subshell. In the d˜s-subshell, for each configuration [Mπ,Mν]d˜s I choose only the most symmetric U˜L˜(6) representations with total pseudo-spin S˜=0. Therefore, all the configurations are given by (0Y0˜) {4P2Y˜} and (0Y0−20˜) {4P+12Y−2˜} for 76Ge and 76Se, respectively with Y = 6−(nν − nπ)/2 and P = (4 − nπ)/2. I derive an explicit expression for the NME of the 2νββ(0+ → 0+) in the closure approximation.