The high-spin structure of the neutron-rich 204Tl isotope has been studied up to a 11.2-MeV excitation energy and a I=30 spin range using the deep-inelastic heavy-ion γ-spectroscopy method with reactions of 48Ca on thick 208Pb and 238U targets. The established structure of yrast levels involves four isomeric states up to Iπ=22-, the highest spin state available for the maximally aligned four valence holes. The observations are interpreted and quantitatively confirmed by shell-model calculations. The rates of the identified M2 and E3 isomeric decays are discussed and a striking analogy is found for the yrast level structures and γ decays observed in the 18+ to 22- and 45/2- to 53/2+ spin ranges in 204Tl and 203Hg, respectively. In the highest spin part of the scheme, two prominently populated yrast states are tentatively identified as the 3 - 208Pb core excitation built on the 22- and 20 + maximally aligned four-hole states. Their energies are reproduced well by using energy shifts observed in experiments for the 208Pb core octupole excitation coupled to simpler intrinsic structures
