Mutually exclusive types allowing all properties

Question

I am writing a type for nested routes array. The array can contain either a prefixed routes object or a simple route object.

The conditions are:

1. If it is a simple route object, then it must contain only the properties that are mentioned in IApiRoute.
2. If it is a prefixed route object that it must contain two keys only
   2 a. First key is prefix as mentioned in IPrefixApiRoute.
   2 b. Second key is routes array, it can contain an array of objects mentioned in point 2 and point 1.

I have created the typings, but there is a problem, it is not giving a compile time error if I create an object like this

const array: Array<IRawApiRoute> = [
    {
        prefix: "auth",
        routes: [],
        method: "GET", // This key shouldn't be allowed here, as this object can contain only the keys from IPrefixApiRoute
    },
];

The typings that I have prepared are:

type Method = "GET" | "DELETE" | "HEAD" | "OPTIONS" | "POST" | "PUT" | "PATCH";

interface IApiRoute {
    route: string;
    method: Method;
    routeParams: string[];
    queryParams: string[];
    name: string;
}

interface IPrefixApiRoute {
    prefix: string;
    routes: Array<IRawApiRoute>;
}

type IRawApiRoute = IApiRoute | IPrefixApiRoute;

I can't seem to figure out the problem. Any help would be appreciated. Thanks