Oral title: A pile-up of mm sized particles in the disk around Sz 91

Oral abstract: I present ALMA observations of the transition disk Sz 91 indicating that this system might be in the process of 
forming giant planets. The large dust grains are located in a narrow ring as the result of radial drift and dynamical clearing. The 
inner cavity at mm wavelengths is much larger than at IR wavelengths providing clear evidence for dust filtering and we detect gas 
inside the dust cavity.