https://bgt-48.blogspot.com/2018/02/powershellxml-xmltextwriter.html
$xmldoc = [xml](Get-Content "c:\temp\books.xml")
$encod = [System.Text.Encoding]::UTF8
$xmlwriter= New-Object System.Xml.XmlTextWriter("c:\temp\books.xml", $encod)
$xmlwriter.Formatting = [System.Xml.Formatting]::Indented
$xmlwriter.IndentChars = "`t"
$xmldoc.Save(xmlwriter)
$xmlwriter.Close()