We have our own in house tiling team.
Floor primed with acrylic primer prior to laying de-mat to separate all tiled areas from the screed. Once de -mat installed with a acrylic based glue.  Then joints covered with a joint tape and then is ready for tiling.
This then means all tiling is separated from screed and have full expansion throughout all tiled areas which works with underfloor heating.
When all that is complete tiling can commence.