Wiktionary
adv. (context idiomatic English) An emphatic form of "believe me"; you [the subject] had better believe me [the speaker].
Wikipedia
Believe You Me (1985) is the third album by Blancmange and was released in 1985. A remastered edition was released by Edsel in 2008 which featured the album along with 4 bonus tracks.
Usage examples of "believe you me".
But believe you me, when we get to where the robots are shooting at us, you'll be mighty sorry if you ain't got something purple to put on.
But believe you me, when we get to where the robots are shooting at us, you’.
If I have anything to say about the peace settlement after the war, I'd be sending plenty of Danes to the chopping block, believe you me.
When it chances upon something convenient, believe you me, it.
I don't dispute that it was tricky, but believe you me, Demy ….
When it chances upon something convenient, believe you me, it'll attack.
The southrons don't have to go through this sort of nonsense when they move their troops from hither to yon, believe you me they don't.