DigiKam and Pentax RAW with xmp sidecar

Hello

I am using Digikam 5.8.0 on Windows10. I am using the raw format from Pentax with xmp-sidecars.
The picture and the xmp file itself was generated by Lightroom.

I have now the problem that digiKam can read the PEF-File but does not recognize the xmp-file.
If I export the pef-File to an dng-file type (with Lightroom) digiKam is able to read the xmp-file.

Is there an compatibility problem? What can I do?

Greetings

Gerhard