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 $M_star = 1.00pm0.03,mathrm{M_odot}$ and $R_star = 1.09pm0.03,mathrm{R_odot}$, 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.
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