Context :

Aims : In this work , we characterize the low mass companion of the A0 field star HR 3549 .

Methods : We observed HR 3549AB in imaging mode with the the NIR branch ( IFS and IRDIS ) of SPHERE @ VLT , with IFS in YJ mode and IRDIS in the H band .
We also acquired a medium resolution spectrum with the IRDIS long slit spectroscopy mode .
The data were reduced using the dedicated SPHERE GTO pipeline , purposely designed for this instrument .
We employed algorithms such as PCA and TLOCI to reduce the speckle noise .

Results : The companion was clearly visible both with IRDIS and IFS .
We obtained photometry in four different bands as well as the astrometric position for the companion .
Based on our astrometry , we confirm that it is a bound object and put constraints on its orbit .
Although several uncertainties are still present , we estimate an age of \sim 100-150 Myr for this system , yielding a most probable mass for the companion of 40-50M _ { \mathrm { Jup } } and T _ { eff } \sim 2300 - 2400 K. Comparing with template spectra points to a spectral type between M9 and L0 for the companion , commensurate with its position on the color-magnitude diagram .

Conclusions :