Through an in-beam study of the Tm-153(69)84 nucleus we have identifie
d the pih11/2(5)nuf7/2(2) and pih11/2(5)nuf7/2h9/2 7-valence particle
configurations up to their fully aligned spins of 47/2- and 51/2-. She
ll model calculations predict that in the pih11/2(5)nuf7/2h9/2 configu
ration, contrary to the pih11/2(5)nuyf7/1(2) case, the h11/2 proton se
niority does not increase regularly with spin. This seniority inversio
n is verified by the data.