US-based credit card company American Express (Amex) has joined peer MasterCard as an investor in Izettle, a Sweden-based mobile payment system (whose staff are pictured).

Amex provided an undisclosed amount to join Izettle’s series B round that initially closed last year at €25m ($32m).

Alongside the two card companies in the B round are local bank SEB’s Private Equity unit and venture capital firms Greylock Partners, Northzone Ventures, Creandum and Index Ventures.

Index and Creandum had provided about $15m in…