Context : HD 46375 is known to host a Saturn-like exoplanet orbiting at 0.04 AU from its host star .
Stellar light reflected by the planet was tentatively identified in the 34-day CoRoT run acquired in October-November 2008 .

Aims : We constrain the properties of the magnetic field of HD 46375 based on spectropolarimetric observations with the NARVAL spectrograph at the Pic du Midi observatory .
In addition , we use a high-resolution NARVAL flux spectrum to contrain the atmospheric parameters .
With these constraints , we perform an asteroseismic analysis and modelling of HD 46375 using the frequencies extracted from the CoRoT light curve .

Methods : We used Zeeman Doppler imaging to reconstruct the magnetic map of the stellar surface .
In the spectroscopic analysis we fitted isolated lines using 1D LTE atmosphere models .
This analysis was used to constrain the effective temperature , surface gravity , and chemical composition of the star .
To extract information about the p-mode oscillations , we used a technique based on the envelope autocorrelation function ( EACF ) .

Results : From the Zeeman Doppler imaging observations , we observe a magnetic field of \approx 5 gauss .
From the spectral analysis , HD 46375 is inferred to be an unevolved K0 type star with high metallicity { [ Fe / H ] } = +0.39 .
Owing to the relative faintness of the star ( m _ { \mathrm { hip } } = 8.05 ) , the signal-to-noise ratio is too low to identify individual modes .
However , we measure the p-mode excess power and large separation \Delta \nu _ { 0 } = 153.0 \pm 0.7 \mu Hz .

Conclusions : We are able do constrain the fundamental parameters of the star thanks to spectrometric and seismic analyses .
We conclude that HD 46375 is similar to a young version of \alpha Cen B .
This work is of special interest because of its combination of exoplanetary science and asteroseismology , which are the subjects of the current Kepler mission and the proposed Plato mission .