Searches for new physics with heavy flavour at ATLAS

The Flavour Changing Neutral Current processes are sensitive to New Physics contributions, in particular through additional electroweak loop amplitudes. The angular analysis of the decay of $B^0\to \mu^+\mu^-K^{*0}$ is presented. A number of angular coefficients are measured as a function of the invariant mass squared of the dimuon system using data collected by the ATLAS experiment at the LHC. Comparison is made to theoretical predictions, including for the observable $P_5^\prime$, for which there has been recent tension between theory and experiment. ATLAS result on the study of the $B^0_{(s)}\to\mu^+\mu^-$ rare decays is also presented.