He crowned two Hungarian monarchs, Ladislaus II and Stephen IV king, because Lucas, Archbishop of Esztergom, who considered them as usurpers, had denied to perform the ceremony.

He featured a similar function in the next year, March 1157, when Gervasius, Bishop of Győr interceded with Géza II to grant the collection right of salt duties to the archdiocese of Esztergom at Nána and Kakat (present-day Štúrovo, Slovakia).

According to another non-authentic charter, Mikó hosted Géza II and several other prelates in his archiepiscopal see, Bács (present-day Bač, Serbia) on Easter 1158.

The forgery claims that Géza, amidst the feast, transliterated Saint Stephen's privilege donations to the Pécsvárad Abbey (as the original document have been destroyed during a fire in 1105).

[3][5] On hearing of Géza's death, Byzantine Emperor Manuel I Komnenos dispatched an army and hastened towards Hungary, because he attempted to extend his suzerainty over the kingdom.

Historian Ferenc Makk considered that the rivalry between the metropolitan sees of Esztergom and Kalocsa, beside the latter's territorial proximity to the Byzantine frontier, also contributed to Mikó's defection to the court of Ladislaus II.

[10] According to historian Gyula Pauler, Stephen III sent Archbishop Mikó, alongside others, to the Byzantine court to negotiate the peace with Emperor Manuel in 1165.