  We realize experimentally an atom-optics quantum chaotic system, the
quasiperiodic kicked rotor, which is equivalent to a 3D disordered system, that
allow us to demonstrate the Anderson metal-insulator transition. Sensitive
measurements of the atomic wavefunction dynamics and the use of finite-size
scaling techniques make it possible to extract both the critical parameters and
the critical exponent of the transition, which is in good agreement with the
value obtained in numerical simulations of the 3D Anderson model.
