Shared Value MD Matthew Hooper and vice-president Anastasia Gorokhova are leading the account, believed to be worth more than £50,000. They report to head of IR Andre Bliznyuk.
The appointment follows a pitch last October which was fiercely contested by the City's top PR firms.
Sistema's listing of general depository receipts, each of which represents 20 per cent of a Sistema share listed in Moscow, is set to raise £826m, and marks a watershed for Russian companies looking for foreign investment.
Shared Value is promoting Sistema, which owns half of eastern Europe's mobile phone operator MTS and Moscow fixed-line company MGTS, as a way for investors to access Russia's developing consumer services sector.