  We present a broadband spectral study of the radio-loud narrow-line Seyfert 1
galaxy 1H~0323+342 based on multi-epoch observations performed with NuSTAR on
2014 March 15, and two simultaneous observations performed with Suzaku and
Swift on 2009 July 26 and 2013 March 1. We found the presence of a strong soft
X-ray excess emission, a broad but weak Fe line and hard X-ray excess emission.
We used the blurred reflection (relxill) and the intrinsic disc Comptonization
(optxagnf), two physically motivated models, to describe the broadband spectra
and to disentangle the disk/corona and jet emission. The relxill model is
mainly constrained by the strong soft X-ray excess although the model failed to
predict this excess when fitted above 3keV and extrapolated to lower energies.
The joint spectral analysis of the three datasets above 3keV with this model
resulted in a high black hole spin ($a>0.9$) and moderate reflection fraction
$R\sim 0.5$. The optxagnf model fitted to the two simultaneous datasets
resulted in an excess emission in the UV band. The simultaneous UV-to-hard
X-ray spectra of 1H~0323+342 are best described by a model consisting of a
primary X-ray power-law continuum with $\Gamma \sim 1.8$, a blurred reflection
component with $R\sim 0.5$, Comptonised disk emission as the soft X-ray excess,
optical/UV emission from a standard accretion disk around a black hole of mass
$\sim 10^7{\rm M_{\odot}}$ and a steep power law ($\Gamma \sim 3-3.5$)
component, most likely the jet emission in the UV band. The fractional RMS
variability spectra suggest that both the soft excess and the powerlaw
component are variable in nature.
