[en] A K^π=8^- strongly coupled rotational band, which is built upon a 23 ns isomeric state, has been established in ¹⁷⁰Hf. The single-particle configuration of the band has been determined from the in-band to out-of-band branching ratios and associated |(g_K-g_R)|/Q₀ values. The γ-ray decay of the K^π=8^- isomeric state proceeds through a K^π=6⁺ intrinsic state, in accordance with the K-selection rule. A complex array of delayed γ-ray transitions have been observed to link this K^π=6⁺, intrinsic bandhead state into the yrast states. In particular, a new ΔK=8, 1141 keV, E1 transition links the K^π=8^- isomeric state directly to the ground-state band. The γ-ray reduced hindrance factor for this E1 decay in ¹⁷⁰Hf is the smallest ΔK=8 transition observed in the Hf nuclei. However, its value is consistent with that expected on the basis of the increased Coriolis mixing which occurs in the lighter Hf isotopes. copyright 1999 The American Physical Society