Good observation. The GeoCellTCMT.xml indeed contains the list of materials for the geocel, Unfortunately, this is a left over from the CDB publication by Terra Vista and is not part of the CDB standard. As such, you cannot rely on this file to get the list of materials. Terra Vista 19 is now removing this file from its CDB publication.
Ok. Thank you Herman.
In the sample terrains Yemen and Pendleton, in the root of the dataset 006_RMDescriptor, there is a file called GeoCellTCMT.xml.
It seems to contain the list of the materials for the current GeoCell.
However I did not find any mention of it in the specifications.
Is it actually part of the standard ? Can I rely on this file to find the list of the materials for a GeoCell ?