Both igen ~ gigen ~ gen 'again, also' and tu 'too, also' are used as focus particles. They do not have to appear adjacent to the focused element. Igen also has a use like English 'again’ (its source) and like English 'yet’, e.g.
Thets anatha lengguij igen fo mibala.
'That’s yet another way of saying it.’ (ES03_A01_02).
Source: Angelo et al. 1998
Source: Angelo et al. 1998
Source: Angelo et al. 1998