Access Sage CRM relationship data via Rest API (sdata)

SOLVED

Is there a way to acces and update Sage CRM relationship data? We use the Rest API interface (sdata in version 2022 R2) to access company and person data. In the user interface we use relationships to do company-company relationships. In the Sage CRM database this results in updates in table RelatedEntitydata (and RelatedEntitylinks).

I tried to access these relationships via Rest API, but did not succeed.
Is there anybody with information on how to access the relationships via Rest API?