Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: chairperson, currency, employer, member of

Prime Minister Alexis Tsipras resigned last week after his acceptance of an €86 billion rescue package for Greece's stricken economy triggered a major rebellion within his radical left Syriza party.
chairperson