Prolate-oblate shape coexistence close to the ground state in the strongly-deformed proton-richA≈120nuclei is reported for the first time. One of the four reported bands in119Cs, built on a11/2?state at 670 keV, consists of nearly degenerate signature partners, and has properties which unequivocally indicate the strongly-coupledπh11/2[505]11/2?configuration associated with oblate shape. Together with the decoupledπh11/2[541]3/2?band built on the11/2?prolate state at 110 keV, for which a half-life ofT1/2=55(5)μshas been measured, the new bands bring evidence of shape coexistence at low spin in the proton-rich strongly deformedA≈120nuclei, a phenomenon predicted since long time, but not yet observed. Calculations using the particle-number conserving cranked shell model and two dimensional tilted axis cranking covariant density functional theory support and well reproduce the observed oblate and prolate coexisting low-energy states in119Cs.
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