We derive a 2 + 1 dimensional model with unconventional supersymmetry at the boundary of an AdS 4 N -extended supergravity, generalizing previous results. The (unconventional) extended supersymmetry of the boundary model is instrumental in describing, within a topdown approach, the electronic properties of graphene-like 2D materials at the two Dirac points, K and K . The two valleys correspond to the two independent sectors of the OSp(p|2)×OSp(q|2) boundary model in the p = q case, which are related by a parity transformation. The Semenoff and Haldane-type masses entering the corresponding Dirac equations are identified with the torsion parameters of the substrate in the model.