How to make two unique fields in a schema

schema: {
teamOnBranch: {
        fields: {
          teamId: {
            type: "string",
            required: true,
            references: {
              model: "team",
              field: "id",
            },
          },
          branchId: {
            type: "string",
            required: true,
            references: {
              model: "branch",
              field: "id",
            },
          },
          assignedAt: {
            type: "date",
            required: true,
          },
        },
      },
}