Pure powdered compounds with a general formula Th1-xErx-(SiO4)(1-x)(PO4)(x) belonging to the zircon-xenotime family were successfully synthesized under hydrothermal conditions (250 degrees C, 7 days) as recently reported for the preparation of coffinite. Therefore, a thorough, combined PXRD, EDX, EXAFS, Raman, and FTIR analysis showed the formation of a solid solution in agreement with Vegard's law. Moreover, the examination of the local structure shows that the Th-O distances remain close to those found in ThSiO4, whereas the Er-O distances show a significant decrease from 2.38(14) to 2.34(7) angstrom when increasing the erbium content from x = 0.2 to x = 1. The variation of the local structure also affects the PO43- groups that are surely distorted in the structure.