sylorimba
xylo-marimba
marimba-xylophone

As the xylorimba (or, less commonly, the xylo-marimba) it has been called for in a number of 20th-century classical works.

The xylorimba (sometimes referred to as xylo-marimba or marimba-xylophone) is a pitched percussion instrument corresponding to a xylophone with an extended range (and not to a combination of a xylophone with a marimba, as the name might suggest).