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The structure of graphite-adsorbed n-alkanes for 10 ≤ n ≤ 20 has been investigated by SAXS. Below the bulk melting point, Tm, and for alkanes with even n, two distinct diffraction peaks are observed, one associated with the bulk and the other with the surface structure. For alkanes with odd n, only one peak is observed below Tm; above Tm a significant reduction in intensity is found, indicating melting of the bulk, but a peak remains. The intensity at Tm increases with n and correlates with previous pyknometric and calorimetric measurements. The surface-adsorbed structure has a repeat corresponding to the orthorhombic spacing of the bulk alkane crystal.