In the context of the input sentence, determine the relationship between 'Syriza' and 'Alexis Tsipras'.
Options: member of, chairperson, distribution format, 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