What should the worshiper do if he finishes reciting Al-Fatiha in a loud prayer and the imam has not yet begun reciting after it?

The Imam is prohibited from long silences between Al-Fatiha and the surah. What is prescribed is a light pause, to allow the congregant to begin reciting Al-Fatiha. If the Imam remains silent for a long time, the congregant should recite Al-Fatiha and a surah after it until the Imam begins his recitation, then the congregant should become silent, because it is not permissible for the congregant to recite while the Imam is reciting, except for Al-Fatiha.