2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/29886We consider the Ashkin-Teller model with negative four-spin coupling but still in the region where the ground state is ferromagnetic. We establish the standard Lebowitz inequality as well as the extension that is necessary to prove a divergent susceptibility.Ams-TeX, 12 pages; two references added, final version accepted for publication in Physica AStatistical Mechanicstext