There isn’t a good tax-advantaged alternative if you’re an employee with access to a 401k. If you’re under the income limit, you can make deductible contributions to an traditional IRA but that’s capped at $5500 per year vs $18,000 for the 401k. Plus there’s no company match there. The best practice is to contribute to your 401k up to the employer match and then contribute the rest to an IRA. Once you’re at the IRA limit you comtribute the rest to the 401k.