We claim the ornamental design for a sample holder for an electron microscope, as shown and described.
FIG. 1 is a front, top and right side perspective view of a sample holder for an electron microscope showing our/my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines in FIGS. 2-5 and 7 views are included for the purpose of illustrating a portion of the sample holder for an electron microscope that forms no part of the claimed design.