The ornamental design for a sheetmaterial with octagonalsurface pattern, as shown and described.
The sole FIGURE is a view of the sheet material with octagonal surface pattern, showing our new design; and
The bottom surface of the sheet material with octagonal surface pattern is plain and unornamented.
The claimed design is a two-dimensional pattern applied to sheet material surfaces such as clothing, fabrics, piece goods, bedding, and similar surfaces. The broken line boundary forms no part of the claimed design.