var
Contenido: TStringStream;
begin
...
RQFile.Method := TRESTRequestMethod.rmPOST;
Contenido := TStringStream.Create;
try
Contenido.LoadFromFile('Fichero.xml'); RQFile.Body.Add(Contenido, TRESTContentType.ctTEXT_PLAIN);
RQFile.Execute;
jValue := RRFile.JSONValue;
Memo2.Text := jValue.ToString
finally
contenido.Free;
...
end;