A charge-transfer salt consisting of 1,1′-dioctyl-4,4′-bipyridinium and bis(maleonitriledithiolato)nickelate is described. Its crystal is built from mixed stacks of the anion and cation, with the anions (A) and cations (C) adopting an …ACAC… fashion within a stack. This salt shows a novel non-ferroelectric-type dielectric phase transition at around 324 K and bistability.