  We present the discovery and characterization of a new transiting planet from
Campaign 17 of the Kepler extended mission K2. HD 119130 b is a warm
sub-Neptune on a 17-d orbit around a bright (V = 9.9 mag) solar-like G3 V star
with a mass and radius of $M_\star = 1.00\pm0.03\,\mathrm{M_\odot}$ and
$R_\star = 1.09\pm0.03\,\mathrm{R_\odot}$, respectively. We model
simultaneously the K2 photometry and CARMENES spectroscopic data and derive a
radius of $R_\mathrm{p} = 2.63_{-0.10}^{+0.12}\,\mathrm{R_\oplus}$ and mass of
$M_\mathrm{p} = 24.5_{-4.4}^{+4.4}\,\mathrm{M_\oplus}$, yielding a mean density
of $\rho_\mathrm{p} = 7.4_{-1.5}^{+1.6}\,\mathrm{g\,cm^{-3}}$, which makes it
one of the densest sub-Neptune planets known to date. We also detect a linear
trend in radial velocities of HD 119130 ($\dot{\gamma}_{\rm RV}=
-0.40^{+0.07}_{-0.07}\,\mathrm{m\,s^{-1}\,d^{-1}}$) that suggests a long-period
companion with a minimum mass on the order of $33\,\mathrm{M_\oplus}$. If
confirmed, it would support a formation scenario of HD 119130 b by migration
caused by Kozai-Lidov oscillations.
