Search for Signature Inversion in πi_13/2 vi_13/2 Band in Odd-Odd ¹⁷⁸Ir

Search for the πi_13/2 vi_13/2 band in ¹⁷⁸Ir have been conducted through the ¹⁵²Sm(³¹P,5nγ)¹⁷⁸Ir reaction and the excitation functions, x-γ and γ-γ-t coincidence measurements. Five rotational bands have been newly identified. The low-spin signature inversion in the πi_13/2 vi_13/2 band has been confirmed by the observations of linking transitions and signature crossing at I = 25.5ħ. The inversion phenomenon in πh_11/2 vi_13/2, πh_9/2 vi_13/2, and πh_13/2 vi_13/2 structures in ¹⁷⁸Ir provides a unique testing ground for different theoretical interpretations.