High-spin states and collective oblate bands in ¹³⁹Nd

High spin states in ¹³⁹Nd nucleus have been reinvestigated with the reaction ¹²⁸Te (¹⁶O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2ℏ. At low spin, the yrast collective structure built on the νh_11/2^-1 multiplet shows a triaxial shape with γ≈32^° according to calculations of the triaxial rotor-plus-particle model. The configurations for some high spin states have been discussed from a systematic comparison with neighboring nuclei. Three collective oblate bands with γ~-60^° at high spin were identified for the first time. A band crossing is observed around ℏω~0.4 MeV in one oblate band based on the 25/2^- level. The characteristics for these oblate bands have been discussed.