My home directory has aquired an unrecognised folder

An unrecognised folder called /home/peter/party invite.odt_FILES has appeared on my home directory. I have no idea where it comes from except that the is a document called partyinvite.odt already in the home directory. When I open
/home/peter/party invite.odt_FILES I find 7 listings, including

This XML file does not appear to have any style information associated with it. The document tree is shown below.

      <rdf:Description rdf:about="styles.xml"></rdf:Description><rdf:Description rdf:about=""><ns0:hasPart rdf:resource="styles.xml"/></rdf:Description><rdf:Description rdf:about="content.xml"><rdf:type rdf:resource="http://docs.oasis-open.org/ns/office/1.2/meta/odf#ContentFile"/></rdf:Description><rdf:Description rdf:about=""><ns0:hasPart rdf:resource="content.xml"/></rdf:Description><rdf:Description rdf:about=""><rdf:type rdf:resource="http://docs.oasis-open.org/ns/office/1.2/meta/pkg#Document"/></rdf:Description></rdf:RDF>

followed by other similar entries one of which is several pages long.

Have I been hacked, or is it finger trouble? I am on Ubuntu 16.04 LTS after an upgrade. Sometimes the computer is slow but this varies. All advice greatly appreciated.

Peter Ratcliffe