Context :

Aims : We focus on the kinematical properties of a proto-binary to study the infall and rotation of gas towards its two protostellar components .

Methods : We present ALMA Science Verification observations with high-spectral resolution of IRAS 16293-2422 at 220.2 GHz .
The wealth of molecular lines in this source and the very high spectral resolution offered by ALMA allow us to study the gas kinematics with unprecedented detail .

Results : We present the first detection of an inverse P-Cygni profile toward source B in the three brightest lines .
The line profiles are fitted with a simple two-layer model to derive an infall rate of 4.5 \times 10 ^ { -5 } M _ { \odot } { yr ^ { -1 } } .
This infall detection would rule-out the previously suggested possibility that source B is a T Tauri star .
A position velocity diagram for source A shows evidence of rotation with an axis close to the line-of-sight .

Conclusions :