  Soft X-ray resonant powder diffraction has been performed at the Mn L2,3
edges of A-site ordered SmBaMn2O6. The energy and polarization dependence of
the (1/2 1/2 0) reflection provide direct evidence for a (x2-z2)/(y2-z2) type
orbital ordering in contrast to the single layer manganite. The temperature
dependence of the reflection indicates an orbital reorientation transition at
210 K, below which the charge and orbital ordered MnO2 sheets show AAAA type of
stacking. The concurring reduction of the ferromagnetic super exchange
correlations leads to further charge localization.
