(New-Object DirectoryServices.DirectorySearcher("(&(objectCategory=group)(name=Domain Admins))")) .FindAll().Properties['Member']
Working better with output: (function from https://petri.com/expanding-active-directory-searcher-powershell/)
Function Convert-ADSearchResult {
[cmdletbinding()]
Param(
[Parameter(Position = 0,Mandatory,ValueFromPipeline)]
[ValidateNotNullorEmpty()]