  We obtain a controlled description of a strongly correlated regime of
electronic behaviour. We begin by arguing that there are two ways to
characterise the electronic degree of freedom, either by the canonical fermion
algebra or the graded Lie algebra su(2|2). The first underlies the Fermi liquid
description of correlated matter, and we identify a novel regime governed by
the latter. We exploit an exceptional central extension of su(2|2) to employ a
perturbative scheme recently developed by Shastry, and obtain a series of
successive approximations for the electronic Green's function. We then focus on
the leading approximation, which reveals a splitting in two of the electronic
dispersion. The Luttinger sum rule is violated, and a Mott metal-insulator
transition is exhibited. We offer a perspective.
