  The fractional quantum Hall (FQH) effect at filling factor v = 5/2 has
recently come under close scrutiny, as it may possess quasi-particle
excitations obeying nonabelian statistics, a property sought for topologically
protected quantum operations. Yet, its microscopic origin remains unidentified,
and candidate model wave functions include those with undesirable abelian
statistics. Here we report direct measurements of the electron spin
polarization of the v = 5/2 FQH state using resistively detected nuclear
magnetic resonance (NMR). We find the system to be fully polarized, which
unambiguously rules out the most-likely abelian contender and thus lends strong
support for the v = 5/2 state being nonabelian. Our measurements reveal an
intrinsically different nature of interaction in the first-excited Landau level
underlying the physics at v = 5/2.
