A sellers financial institution identifier scheme MUST be BIC if the scheme of the account identifier is IBAN and the payment means type is international account transfer
//cac:PaymentMeans(cac:PayeeFinancialAccount/cac:FinancialInstitutionBranch/cac:FinancialInstitution/cbc:ID/@schemeID='BIC') and (cac:PayeeFinancialAccount/cbc:ID/@schemeID = 'IBAN') or not(cac:PayeeFinancialAccount/cbc:ID/@schemeID = 'IBAN')