Is it permissible for the preacher to add to the formula of "Assalamu Alaikum" when greeting the worshippers, based on other absolute narrations regarding the formula of greeting?

Scholars have differed regarding the ruling on the preacher (khatib) greeting the congregants when he ascends the minbar. The preponderant opinion is that it is a Sunnah established from the Prophet, peace and blessings be upon him. As for the manner of his greeting, it has been generally reported that he would greet when he ascended the minbar. A mursal narration states that he would turn his face towards the people and say, "Assalamu alaykum." If this narration is authentic, then it clarifies the manner of the greeting. If it is not authentic, then the greeting remains general, and any valid form of greeting is permissible.