  The first-forbidden beta-decay of 17Ne into the 'halo' state J=1/2+ of 17F
presents one of the largest measured asymmetries for mirror beta-decay feeding
bound final states. This asymmetry is studied in the framework of the Shell
Model Embedded in the Continuum (SMEC). The spatial extent of single particle
orbits is constrained by the proton capture cross-section 16O(p,gamma)17F
calculated in SMEC . This allows to estimate the mirror symmetry breaking in
17F/17O and 17Ne/17N nuclei.
