Brex, the corporate card for startups, is integrating with expense-management giant SAP Concur and accounting software Xero as it aims to grow alongside its customers who are maturing out of the startup segment and looking for enterprise-grade solutions. For Brex, it's also a step toward competing with Amex over larger customers. Amex also has a corporate card for startups that it launched in October last year. And fellow fintechs Divvy and Ramp are also competing with Brex in the startup space. Visit Business Insider's homepage for more stories.