The IRS position on the student loan interest deduction is that a taxpayer must (1) be legally obligated to pay interest on the loan and (2) must have actually paid the interest.
If, as I infer from the information in your question, your ex-husband has been legally obligated to make the payments by a final divorce decree issued by a court, he would appear to meet the first requirement. If he is actually making the payments, he meets the second requirement. He should be entitled to the deduction.
While the loans may still be in your name, you would not be able to take the deduction, since you are not actually making the payments.
For more information, please see IRS Pub. 970 Tax Benefits for Education, Chapter 4.
Enter your E-mail address. We'll send you an e-mail with instructions to reset your password.