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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.
Wonderboard durock and permabase.
Lightweight cement based overlays mimic stone brick and other wall textures placing overlays over tile floors by chris sullivan chemsystems inc.
Cement board and fiber cement board.
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.
Examples of fiber cement board.
These come in two categories.