Wonderboard durock and permabase.
Cement over tile floor.
Another and i think better way would be to use a self leveling concrete that can be aplied in a much thinner coat and if head room is a problem would be of help.
Examples of fiber cement board.
Lightweight cement based overlays mimic stone brick and other wall textures placing overlays over tile floors by chris sullivan chemsystems inc.
Get free shipping on qualified tile mortar or buy online pick up in store today in the flooring department.
If you were to use conventional concrete i would say you should pour a minimun of 3 inches both for strength and to ease leveling.
Mainly the products i m talking about are considered to be cement backer boards for tile installation.
Examples of cement board are.