First you need to know the reason for which the company is asking you to indemnify them. merely by sending abroad, the company cannot claim the said amount. further, did u complete the project for which the company sent you abroad. was the project fully satisfied in terms of the money spent by the company on you?
this is legal if the company has made you sign the bond for which u state that u shall not leave the company etc or any of these terms. If they are denying to show the details, then send a legal notice to them asking them to state the reasons and give the entire calculations. If need be make a representation to higher authorities and try to settle the matter amicably.