Dear Urvashi,Now a days this is happening in every organisation; I can understand your position being a single HR as I am in the same boat. I feel 1st you take their immediate superior in confidednce and check their opinion about these guys performance, interpersonal relationships within organisation. If they are also feeling it and sensing that performance and even team bonds are getting hampered then ask them only to initiate a talk with them by calling one to one meeting. You need to be apart of such meeting.After such meeting observe wether there are improvements or not and then after a gap of 15 days along with their immediate superior have meeting them one by one and convey the message that management is looking at this very seriously and we will observe the improvements for next 15 days again and will imform you accordingly.If there is a desirable change then situation is under control then convey the same message to that employee as well because appriciation is beiggest imp tool in HR to make people realised about their progress on professional front.But if you found that situation is twisted in more wrost phenomenon then you issue them waring letter and this will legally help you to take further serious action against them.Regards,Mona