Can I sue my former employer for making slanderous and defamatory accusations about me?

Yes, you can sue [you would include the company also] but you have to show it was untrue and not just an opinion as opposed to a statement of fact. So if your supervisor said "M stole a computer" you would have a case, but not if he said, "I think M is too forgetful to be a good employee." You also have to show you were fired because of those statements. If there is some type of grievance procedure at work, you should go through that first. Why did they first transfer you instead of firing you from your initial position?