  We analyse the collective behavior of a mean-field model of phase-oscillators
of Kuramoto-Daido type coupled through pairwise interactions which depend on
phase differences: the coupling function is composed of three harmonics. We
provide convincing evidence of a transient but long-lasting chaotic collective
chaos, which persists in the thermodynamic limit. The regime is analysed with
the help of clever direct numerical simulations, by determining the maximum
Lyapunov exponent and assessing the transversal stability to the
self-consistent mean field. The structure of the invariant measure is finally
described in terms of a resolution-dependent entropy.
