org-publish-sitemap-file-entry-format

org-publish-sitemap-file-entry-format is a variable defined in `ox-publish.el'.
Its value is

"%t"

Documentation:
Format string for site-map file entry.
You could use brackets to delimit on what part the link will be.

%t is the title.
%a is the author.
%d is the date formatted using `org-publish-sitemap-date-format'.

You can customize this variable.