Are the four rak'ahs before Dhuhr, which are equivalent to the night vigil - "Salat al-Sahar" - to be prayed with one tasleem or two by two?

It has been reported that the four rak'ahs before Dhuhr prayer are performed with a single tasleem, not with a tasleem between them. These rak'ahs are when the gates of heaven are opened, and it is beloved for a righteous deed to ascend during them. It has also been reported that they are equivalent to night vigil (qiyam al-layl). Ibn Mas'ud used to pray eight rak'ahs after zawwal (midday) and say that they were equivalent to the same number of rak'ahs of night vigil, because midday corresponds to midnight, and both are times of seeking closeness [to Allah] and mercy.