Assalaamu alaykum. The noble prophet, sallallaahu ʻalayhi wa sallam, said (what means) that one should make Adhkaar (plural of Dhikr: expressions of remembrance of Allaah) before having sexual intercourse with his wife, and he stated that it would keep the devil far from the children and that Allaah blesses one during such intimacy. So I want to ask, are there other reasons for the Adhkaar too, apart from the ones I just mentioned? This is because someone said that saying such Adhkaar would make it impossible for jinn to have intercourse with one's wife. Is this authentic, sir?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

Some scholars referred to the reason that that person mentioned to you. Ibn ʻUthaymeen wrote, “Shaytaan (the devil) is present with the son of Aadam (Adam) in all his affairs; when he wants to eat, he is present with him; when he wants to drink, he is present with him, and when he wants to have sexual intercourse with his wife, he is present with him to join him; as in the verse: {...and become a partner in their wealth and their children...} [Quran 17:64]...” [Sharh Riyaadh As-Saaliheen]

Ibn ʻUthaymeen also wrote, “If the man does not mention the name of Allaah (before having intercourse with his wife), Shaytaan may harm their child, and he may join him in enjoying his wife; Allaah, The Exalted, says (what means): {...and become a partner in their wealth and their children...} [Quran 17:64] Some scholars said that becoming a partner in children means that if the man does not mention the name of Allaah before having sexual intercourse, Shaytaan my take part in enjoying his wife...” [Ash-Sharh Al-Mumti’]

Allaah knows best.