The aim of the present proposal is to experimentally investigate the magnetic order below Tc in the cubic quasicrystal approximant Au5.027Si1.307Tb, which orders ferro- or ferrimagnetically below Tc= 10K (Fig. 2). The space group of the atomic structure is Im-3 with a=14.7 Å. In order to get reliable data for detailed analysis, it is important to use WISH which is optimized for measuring magnetic long-range order of complex structures with large unit cells. Because Tb gives such big moments, we ask for GEM as a backup alternative.As far as the magnetism of quasicrystals, no long range magnetic order but only spin-glass like freezing has been observed to date. The approximant Au5.027Si1.307Tb could provide the first determination of a long-range ordered magnetic structure in a quasicrystal approximant and insight into the possible magnetic interactions in related quasicrystals.