This is only possible if you set the NVARCHAR value as XML like below.
declare @a nvarchar(max)
set @a = N'<root><name> SQL Server 2012</name></root>'
select cast(@a as xml)
It will not be meaningful to have XML as '%' as this is not syntactivally correct for having an XML value.
Rahul
Website: http://borngeek.in