Do I have a deflamation of charactor suit?

The company from which I was fired allows employees to take home certain scrap items (pallets)with a properly signed form. I had the properly signed form to remove some scrap pallets, I made a copy of this form (for my records) and turned in the copy to the guard, keeping the original copy. I was terminated for theft. I had permission, so in my mind there is NO theft. I understand that TN is an "at will" state. Seeing how this "theft" accusation will follow me everywhere I look for employment, can I sue for defamation of character or libel?