  We present first-principles multiband spin susceptibility calculations within
the random-phase approximation for four isostructural superconducting
PuCoIn$_5$, PuCoGa$_5$, PuRhGa$_5$, and nonsuperconducting UCoGa$_5$ actinides.
The results show that a strong peak in the spin-fluctuation dressed self-energy
is present around 0.5 eV in all materials, which is mostly created by 5$f$
electrons. These fluctuations couple to the single-particle spectrum and give
rise to a peak-dip-hump feature, characteristic of the coexistence of itinerant
and localized electronic states. Results are in quantitative agreement with
photoemission spectra. Finally, we show that the studied actinides can be
understood within the rigid-band filling approach, in which the
spin-fluctuation coupling constant follows the same materials dependence as the
superconducting transition temperature $T_c$.
