Anomalous four and five quasiparticle isomer decays in 174Hf and 175Hf

High-spin isomeric decays in ¹⁷⁴Hf and ¹⁷⁵Hf are found to populate a large number of different quasiparticle structures. Many weak γ-ray transitions are revealed that violate the usual K-selection rules. Analysis of transition hindrance factors shows the importance of K-mixing in the populated levels. The effects of both chance near-degeneracies and Coriolis coupling are separately identified. The role of high- K components in Fermi-aligned "tilted" bands is emphasized. The 4-quasiparticle excitation energies are compared with the sum of the constituent 2-quasiparticle energies.