There is only one file type that uses the .XMT extension:
An XMT file is a template used by XMind, a brainstorming and mind mapping application. It contains a diagram, such as a map, organizational chart, logic chart, timeline, or matrix, with user-defined settings. The file allows users to save a layout of a diagram and replicate it.
The XMT file is similar to the .XMIND file but is designed solely for replication of a layout. You can create an XMT file by selecting.
Updated: September 14, 2016