  Underdoped PrFeAs(O,F), one of the less known members of the 1111 family of
iron-based superconductors, was investigated in detail by means of transport,
SQUID magnetometry, nuclear magnetic resonance (NMR) measurements and
point-contact Andreev-reflection spectroscopy (PCARS). PCARS measurements on
single crystals evidence the multigap nature of PrFeAs(O,F) superconductivity,
shown to host at least two isotropic gaps, clearly discernible in the spectra,
irrespective of the direction of current injection (i.e., along the ab planes
or along the c axis). Additional features at higher energy can be interpreted
as signatures of a strong electron-boson coupling, as demonstrated by a model
which combines Andreev reflection with the Eliashberg theory. Magnetic
resonance measurements in the normal phase indicate the lack of a magnetic
order in underdoped PrFeAs(O,F), while $^{75}$As NMR spin-lattice relaxation
results suggest the presence of significant electronic spin fluctuations,
peaking above $T_{c}$ and expected to mediate the superconducting pairing.
