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We have utilized second harmonic generation (SHG) to disentangle the coupled first-order charge order/structural transition at Tc ～ 281 K in the transition-metal dichalocogenide IrTe2,an exceptional layered material with 3D properties.The data from SHG shows extremely sharp transition in both the cooling and warming processes with less than 0.2 K transition window.Surface electronic symmetries of C3v and S2 are observed in the high temperature and low temperature phases,respectively.Compared to neutron diffraction data for the structural transition (Phys.Rev.B 88 (2013) 115122) and to the electrical resistivity for the microscopic transition (Phys.Rev.B 95(2017)035148),our data indicates the electronic transition at the surface is the precursor to the structural transition.