We have overridden the standard New Account button with our custom "Search First Before You Create" Lightning Component so that this custom functionality will be invoked whenever a user clicks on New from within an account list view, as shown in the following screenshot:

Once the "Search First Before You Create" Lightning Component is invoked, a search page is presented to users that will allow them to enter a company name into a search textbox and click on Search, as shown in the following screenshot:

In this example, we are searching for the company Acme, which already exists as a record in our Salesforce CRM organization. In this scenario, the user is presented with a results table that lists the Acme account records, along with a link that allows the user to navigate to the account record [Navigate to account], as shown in the following screenshot:

In this example, clicking on the [Navigate to account] link redirects the user to the account record Acme, as shown in the following screenshot: