  In this paper we present the detection of a 1.8 M_Jup planet in a 538 day
period trajectory orbiting the metal-poor star HD171028 ([Fe/H]=-0.49). This
planet is the first to be discovered in the context of a HARPS program
searching for planets around metal-poor stars. Interestingly, HD171028 is one
of the least metal-poor stars in the sample. This discovery is placed in the
context of the models of planet formation and evolution.
