What is the relationship between 'Syriza' and 'Alexis Tsipras' in the context of the input sentence.
Options: member of, distribution format, chairperson, business division

ATHENS, Greece — Alexis Tsipras is set to receive the formal mandate later Monday to form a Greek government for the second time, after his left-wing Syriza party unexpectedly won a decisive victory in early national elections.
chairperson