Highly deformed band structures due to core excitations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Xe</mml:mi><mml:mprescripts /><mml:none /><mml:mn>123</mml:mn></mml:mmultiscripts></mml:math>

High-spin states in $^{123}\mathrm{Xe}$ were populated the $^{80}\mathrm{Se}(^{48}\mathrm{Ca}, 5\mathrm{n})^{123}\mathrm{Xe}$ reaction at a beam energy of 207 MeV. $\ensuremath{\gamma}$-ray coincidence events recorded with Gammasphere spectrometer. Four new high-spin bands have been discovered this nucleus. The are compared those calculated within framework cranked Nilsson-Strutinsky and Nilsson-Strutinsky-Bogoliubov models. It is concluded that configurations involve two-proton excitations across $Z=50$ as well excitation neutrons $N=82$ shell gaps resulting large deformation, ${\ensuremath{\varepsilon}}_{2}\ensuremath{\approx}0.30$ $\ensuremath{\gamma}\ensuremath{\approx}{5}^{\ensuremath{\circ}}$.